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css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">部署标准集群</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-5" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">数据迁移</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-6" tabindex="-1" 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css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">监控与告警</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-9" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">故障诊断</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-10" tabindex="-1" 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class="MuiTypography-root MuiTypography-body1 css-1g11p7i">TiDB 工具</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-0-13" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-w8t2sr"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-11fv84e" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">参考指南</div></div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div 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style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">存储引擎 TiKV</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-2" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root 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class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">TiDB 分布式执行框架</div></div></div></div></div></div></li><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/system-variables/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-4" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">系统变量</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/system-variable-reference/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-5" tabindex="-1" 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css-1g11p7i">服务器状态变量</div></div></div></div></div></div></li></a><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-7" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">配置文件参数</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-8" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">CLI</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-9" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">命令行参数</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-10" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">监控指标</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-11" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">权限</div></div></div></div></div></div></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-0-13-12" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-2jyri7"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-11fv84e" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">SQL</div></div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-12-0" tabindex="-1" 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class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">数据类型</div></div></div></div></div></div><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/data-type-overview/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-0" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">数据类型概述</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/data-type-default-values/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-1" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">数据类型默认值</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/data-type-numeric/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-2" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" 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css-1g11p7i">日期和时间类型</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/data-type-string/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-4" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">字符串类型</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/data-type-json/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-5" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">JSON 类型</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/vector-search-data-types/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-2-6" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-gwjyeh"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">向量数据类型</div></div></div></div></div></div></li></a></div></div></ul></li><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-12-3" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">函数与操作符</div></div></div></div></div></div></li><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/clustered-indexes/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-4" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">聚簇索引</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/vector-search-index/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-5" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">向量索引</div></div></div></div></div></div></li></a><a 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class="css-xeut16"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">生成列</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/sql-mode/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-8" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">SQL 模式</div></div></div></div></div></div></li></a><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/stable/table-attributes/"><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" id="left-nav-treeview-0-0-13-12-9" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><div class="MuiBox-root css-f81823"/><div class="css-szjynw"><div class="MuiBox-root css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">表属性</div></div></div></div></div></div></li></a><li class="MuiTreeItem-root css-1p2jk91" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-0-13-12-10" tabindex="-1" style="margin-top:4px;margin-bottom:4px"><div class="css-fhn3dm MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-xeut16"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-1guu2k2" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 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css-1uoa4hf"><div class="MuiTypography-root MuiTypography-body1 css-1g11p7i">术语表</div></div></div></div></div></div></li></a></ul></div></aside><main class="MuiBox-root css-sb2sd0"><div class="MuiBox-root css-w0vdto"><div class="css-1q5cbag"><div class="MuiBox-root css-was4pq"><div class="MuiContainer-root MuiContainer-maxWidthLg MuiContainer-disableGutters doc-content css-5csqms"><div class="markdown-body MuiBox-root css-0"><h1 id="日期和时间类型" style="position:relative">日期和时间类型<a href="#%E6%97%A5%E6%9C%9F%E5%92%8C%E6%97%B6%E9%97%B4%E7%B1%BB%E5%9E%8B" aria-label="日期和时间类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h1><p>TiDB 支持 MySQL 所有的日期和时间类型，包括 <a href="#date-%E7%B1%BB%E5%9E%8B"><code>DATE</code></a>、<a href="#time-%E7%B1%BB%E5%9E%8B"><code>TIME</code></a>、<a href="#datetime-%E7%B1%BB%E5%9E%8B"><code>DATETIME</code></a>、<a href="#timestamp-%E7%B1%BB%E5%9E%8B"><code>TIMESTAMP</code></a> 以及 <a href="#year-%E7%B1%BB%E5%9E%8B"><code>YEAR</code></a>。完整信息可以参考 <a href="https://dev.mysql.com/doc/refman/8.0/en/date-and-time-types.html" target="_blank" referrerpolicy="no-referrer-when-downgrade">MySQL 中的时间和日期类型</a>。</p><p>每种类型都有有效值范围，值为 0 表示无效值。此外，<code>TIMESTAMP</code> 和 <code>DATETIME</code> 类型能自动生成新的时间值。</p><p>关于日期和时间值类型，需要注意：</p><ul><li><p>日期部分必须是“年-月-日”的格式（例如 <code>1998-09-04</code>），而不是“月-日-年”或“日-月-年”的格式。</p></li><li><p>如果日期的年份部分是 2 位数，TiDB 会根据<a href="#%E5%B9%B4%E4%BB%BD%E4%B8%BA%E4%B8%A4%E4%BD%8D%E6%95%B0">年份为两位数的具体规则</a>进行转换。</p></li><li><p>如果格式必须是数值类型，TiDB 会自动将日期或时间值转换为数值类型。例如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> NOW(), NOW()<span class="hljs-operator">+</span><span class="hljs-number">0</span>, NOW(<span class="hljs-number">3</span>)<span class="hljs-operator">+</span><span class="hljs-number">0</span>; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">---------------------+----------------+--------------------+</span> <span class="hljs-operator">|</span> NOW() <span class="hljs-operator">|</span> NOW()<span class="hljs-operator">+</span><span class="hljs-number">0</span> <span class="hljs-operator">|</span> NOW(<span class="hljs-number">3</span>)<span class="hljs-operator">+</span><span class="hljs-number">0</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">---------------------+----------------+--------------------+</span> <span class="hljs-operator">|</span> <span class="hljs-number">2012</span><span class="hljs-number">-08</span><span class="hljs-number">-15</span> <span class="hljs-number">09</span>:<span class="hljs-number">28</span>:<span class="hljs-number">00</span> <span class="hljs-operator">|</span> <span class="hljs-number">20120815092800</span> <span class="hljs-operator">|</span> <span class="hljs-number">20120815092800.889</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">---------------------+----------------+--------------------+</span> </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre></li><li><p>TiDB 可以自动将无效值转换同一类型的零值。是否进行转换取决于 SQL 模式的设置。比如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">show</span> <span class="hljs-keyword">create</span> <span class="hljs-keyword">table</span> t1; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">-------+---------------------------------------------------------------------------------------------------------+</span> <span class="hljs-operator">|</span> <span class="hljs-keyword">Table</span> <span class="hljs-operator">|</span> <span class="hljs-keyword">Create</span> <span class="hljs-keyword">Table</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------+---------------------------------------------------------------------------------------------------------+</span> <span class="hljs-operator">|</span> t1 <span class="hljs-operator">|</span> <span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> `t1` ( `a` <span class="hljs-type">time</span> <span class="hljs-keyword">DEFAULT</span> <span class="hljs-keyword">NULL</span> ) ENGINE<span class="hljs-operator">=</span>InnoDB <span class="hljs-keyword">DEFAULT</span> CHARSET<span class="hljs-operator">=</span>utf8mb4 <span class="hljs-keyword">COLLATE</span><span class="hljs-operator">=</span>utf8mb4_bin <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------+---------------------------------------------------------------------------------------------------------+</span> <span class="hljs-number">1</span> <span class="hljs-type">row</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.00</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">select</span> @<span class="hljs-variable">@sql</span>_mode; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">-------------------------------------------------------------------------------------------------------------------------------------------+</span> <span class="hljs-operator">|</span> @<span class="hljs-variable">@sql</span>_mode <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------------------------------------------------------------------------------------------------------------------------------------------+</span> <span class="hljs-operator">|</span> ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------------------------------------------------------------------------------------------------------------------------------------------+</span> <span class="hljs-number">1</span> <span class="hljs-type">row</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.00</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">insert</span> <span class="hljs-keyword">into</span> t1 <span class="hljs-keyword">values</span> (`<span class="hljs-number">2090</span><span class="hljs-number">-11</span><span class="hljs-number">-32</span>:<span class="hljs-number">22</span>:<span class="hljs-number">33</span>:<span class="hljs-number">44</span>`); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">ERROR <span class="hljs-number">1292</span> (<span class="hljs-number">22007</span>): Truncated incorrect <span class="hljs-type">time</span> <span class="hljs-keyword">value</span>: `<span class="hljs-number">2090</span><span class="hljs-number">-11</span><span class="hljs-number">-32</span>:<span class="hljs-number">22</span>:<span class="hljs-number">33</span>:<span class="hljs-number">44</span>` </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">set</span> @<span class="hljs-variable">@sql</span>_mode<span class="hljs-operator">=</span>``; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">Query OK, <span class="hljs-number">0</span> <span class="hljs-keyword">rows</span> affected (<span class="hljs-number">0.01</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">insert</span> <span class="hljs-keyword">into</span> t1 <span class="hljs-keyword">values</span> (`<span class="hljs-number">2090</span><span class="hljs-number">-11</span><span class="hljs-number">-32</span>:<span class="hljs-number">22</span>:<span class="hljs-number">33</span>:<span class="hljs-number">44</span>`); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">Query OK, <span class="hljs-number">1</span> <span class="hljs-type">row</span> affected, <span class="hljs-number">1</span> warning (<span class="hljs-number">0.01</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">select</span> <span class="hljs-operator">*</span> <span class="hljs-keyword">from</span> t1; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">----------+</span> <span class="hljs-operator">|</span> a <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">----------+</span> <span class="hljs-operator">|</span> <span class="hljs-number">00</span>:<span class="hljs-number">00</span>:<span class="hljs-number">00</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">----------+</span> <span class="hljs-number">1</span> <span class="hljs-type">row</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.01</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre></li><li><p>SQL 模式的不同设置，会改变 TiDB 对格式的要求。</p></li><li><p>如果 SQL 模式的 <code>NO_ZERO_DATE</code> 被禁用，TiDB 允许 <code>DATE</code> 和 <code>DATETIME</code> 列中的月份或日期为零。例如，<code>2009-00-00</code> 或 <code>2009-01-00</code>。如果使用函数计算这种日期类型，例如使用 <code>DATE_SUB()</code> 或 <code>DATE_ADD()</code> 函数，计算结果可能不正确。</p></li><li><p>默认情况下，TiDB 启用 <code>NO_ZERO_DATE</code> SQL 模式。该模式可以避免存储像 <code>0000-00-00</code> 这样的零值。</p></li></ul><p>不同类型的零值如下表所示：</p><table><thead><tr><th align="left">数据类型</th><th align="left">零值</th></tr></thead><tbody><tr><td align="left">DATE</td><td align="left"><code>0000-00-00</code></td></tr><tr><td align="left">TIME</td><td align="left"><code>00:00:00</code></td></tr><tr><td align="left">DATETIME</td><td align="left"><code>0000-00-00 00:00:00</code></td></tr><tr><td align="left">TIMESTAMP</td><td align="left"><code>0000-00-00 00:00:00</code></td></tr><tr><td align="left">YEAR</td><td align="left">0000</td></tr></tbody></table><p>如果 SQL 模式允许使用无效的 <code>DATE</code>、<code>DATETIME</code>、<code>TIMESTAMP</code> 值，无效值会自动转换为相应的零值（<code>0000-00-00</code> 或 <code>0000-00-00 00:00:00</code>）。</p><h2 id="类型定义" style="position:relative">类型定义<a href="#%E7%B1%BB%E5%9E%8B%E5%AE%9A%E4%B9%89" aria-label="类型定义 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><h3 id="date-类型" style="position:relative"><code>DATE</code> 类型<a href="#date-%E7%B1%BB%E5%9E%8B" aria-label="date 类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h3><p><code>DATE</code> 类型只包含日期部分，不包含时间部分。<code>DATE</code> 类型的格式为 <code>YYYY-MM-DD</code>，支持的范围是 <code>0000-01-01</code> 到 <code>9999-12-31</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-type">DATE</span> </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><h3 id="time-类型" style="position:relative"><code>TIME</code> 类型<a href="#time-%E7%B1%BB%E5%9E%8B" aria-label="time 类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h3><p><code>TIME</code> 类型的格式为 <code>HH:MM:SS[.fraction]</code>，支持的范围是 <code>-838:59:59.000000</code> 到 <code>838:59:59.000000</code>。<code>TIME</code> 不仅可用于指示一天内的时间，还可用于指两个事件之间的时间间隔。<code>fsp</code> 参数表示秒精度，取值范围为：0 ~ 6，默认值为 0。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-type">TIME</span>[(fsp)] </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><div class="MuiBox-root css-1weqspv"><div class="MuiPaper-root MuiPaper-elevation MuiPaper-rounded MuiPaper-elevation0 MuiAlert-root MuiAlert-standardInfo MuiAlert-standard css-1bzshic" role="alert"><div class="MuiAlert-icon css-1l54tgj"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="InfoOutlinedIcon"><path d="M11,9H13V7H11M12,20C7.59,20 4,16.41 4,12C4,7.59 7.59,4 12,4C16.41,4 20,7.59 20, 12C20,16.41 16.41,20 12,20M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12A10, 10 0 0,0 12,2M11,17H13V11H11V17Z"/></svg></div><div class="MuiAlert-message css-1xsto0d"><div class="MuiTypography-root MuiTypography-body1 MuiTypography-gutterBottom MuiAlertTitle-root css-m00e13">注意</div><p>注意 <code>TIME</code> 的缩写形式。例如，<code>11:12</code> 表示 <code>11:12:00</code> 而不是 <code>00:11:12</code>。但是，<code>1112</code> 表示 <code>00:11:12</code>。这些差异取决于 <code>:</code> 字符的存在与否。</p></div></div></div><h3 id="datetime-类型" style="position:relative"><code>DATETIME</code> 类型<a href="#datetime-%E7%B1%BB%E5%9E%8B" aria-label="datetime 类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h3><p><code>DATETIME</code> 类型是日期和时间的组合，格式为 <code>YYYY-MM-DD HH:MM:SS[.fraction]</code>。支持的范围是 <code>0000-01-01 00:00:00.000000</code> 到 <code>9999-12-31 23:59:59.999999</code>。<code>fsp</code> 参数表示秒精度，取值范围为 0~6，默认值为 0。TiDB 支持字符串或数字转换为 <code>DATETIME</code> 类型。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">DATETIME[(fsp)] </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><h3 id="timestamp-类型" style="position:relative"><code>TIMESTAMP</code> 类型<a href="#timestamp-%E7%B1%BB%E5%9E%8B" aria-label="timestamp 类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h3><p><code>TIMESTAMP</code> 类型是日期和时间的组合，支持的范围是 UTC 时间从 <code>1970-01-01 00:00:01.000000</code> 到 <code>2038-01-19 03:14:07.999999</code>。<code>fsp</code> 参数表示秒精度，取值范围为 0~6，默认值为 0。在 <code>TIMESTAMP</code> 中，不允许零出现在月份部分或日期部分，唯一的例外是零值本身 <code>0000-00-00 00:00:00</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-type">TIMESTAMP</span>[(fsp)] </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><h4 id="时区处理" style="position:relative">时区处理<a href="#%E6%97%B6%E5%8C%BA%E5%A4%84%E7%90%86" aria-label="时区处理 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h4><p>当存储 <code>TIMESTAMP</code> 时，TiDB 会将当前时区的 <code>TIMESTAMP</code> 值转换为 UTC 时区。当读取 <code>TIMESTAMP</code> 时，TiDB 将存储的 <code>TIMESTAMP</code> 值从 UTC 时区转换为当前时区（注意：<code>DATETIME</code> 不会这样处理）。每次连接的默认时区是服务器的本地时区，可以通过环境变量 <code>time_zone</code> 进行修改。</p><div class="MuiBox-root css-1weqspv"><div class="MuiPaper-root MuiPaper-elevation MuiPaper-rounded MuiPaper-elevation0 MuiAlert-root MuiAlert-standardError MuiAlert-standard css-kdwypz" role="alert"><div class="MuiAlert-icon css-1l54tgj"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ErrorOutlineIcon"><path d="M11 15h2v2h-2zm0-8h2v6h-2zm.99-5C6.47 2 2 6.48 2 12s4.47 10 9.99 10C17.52 22 22 17.52 22 12S17.52 2 11.99 2zM12 20c-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8-3.58 8-8 8z"/></svg></div><div class="MuiAlert-message css-1xsto0d"><div class="MuiTypography-root MuiTypography-body1 MuiTypography-gutterBottom MuiAlertTitle-root css-m00e13">警告</div><p>和 MySQL 一样，<code>TIMESTAMP</code> 数据类型受 <a href="https://zh.wikipedia.org/wiki/2038%E5%B9%B4%E9%97%AE%E9%A2%98" target="_blank" referrerpolicy="no-referrer-when-downgrade">2038 年问题</a>的影响。如果存储的值大于 2038，建议使用 <code>DATETIME</code> 类型。</p></div></div></div><h3 id="year-类型" style="position:relative"><code>YEAR</code> 类型<a href="#year-%E7%B1%BB%E5%9E%8B" aria-label="year 类型 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h3><p><code>YEAR</code> 类型的格式为 <code>YYYY</code>，支持的值范围是 <code>1901</code> 到 <code>2155</code>，也支持零值 <code>0000</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">YEAR</span>[(<span class="hljs-number">4</span>)] </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><p><code>YEAR</code> 类型遵循以下格式规则：</p><ul><li>如果是四位数的数值，支持的范围是 <code>1901</code> 至 <code>2155</code>。</li><li>如果是四位数的字符串，支持的范围是 <code>'1901'</code> 到 <code>'2155'</code>。</li><li>如果是 1~99 之间的一位数或两位数的数字，1~69 换算成 2001~2069，70~99 换算成 1970~1999。</li><li>支持 <code>'0'</code> 到 <code>'99'</code> 之间的一位数或两位数字符串的范围</li><li>将数值 <code>0</code> 转换为 <code>0000</code>，将字符串 <code>'0'</code> 或 <code>'00'</code> 转换为 <code>'2000'</code>。</li></ul><p>无效的 <code>YEAR</code> 值会自动转换为 <code>0000</code>（如果用户没有使用 <code>NO_ZERO_DATE</code> SQL 模式）。</p><h2 id="自动初始化和更新-timestamp-或-datetime" style="position:relative">自动初始化和更新 <code>TIMESTAMP</code> 或 <code>DATETIME</code><a href="#%E8%87%AA%E5%8A%A8%E5%88%9D%E5%A7%8B%E5%8C%96%E5%92%8C%E6%9B%B4%E6%96%B0-timestamp-%E6%88%96-datetime" aria-label="自动初始化和更新 timestamp 或 datetime permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p>带有 <code>TIMESTAMP</code> 或 <code>DATETIME</code> 数据类型的列可以自动初始化为或更新为当前时间。</p><p>对于表中任何带有 <code>TIMESTAMP</code> 或 <code>DATETIME</code> 数据类型的列，你可以设置默认值，或自动更新为当前时间戳。</p><p>在定义列的时候，<code>TIMESTAMP</code> 和 <code>DATETIME</code> 可以通过 <code>DEFAULT CURRENT_TIMESTAMP</code> 和 <code>ON UPDATE CURRENT_TIMESTAMP</code> 来设置。<code>DEFAULT</code> 也可以设置为一个特定的值，例如 <code>DEFAULT 0</code> 或 <code>DEFAULT '2000-01-01 00:00:00'</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t1 ( ts <span class="hljs-type">TIMESTAMP</span> <span class="hljs-keyword">DEFAULT</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span> <span class="hljs-keyword">ON</span> <span class="hljs-keyword">UPDATE</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span>, dt DATETIME <span class="hljs-keyword">DEFAULT</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span> <span class="hljs-keyword">ON</span> <span class="hljs-keyword">UPDATE</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span> </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><p>除非指定 <code>DATETIME</code> 的值为 <code>NOT NULL</code>，否则默认 <code>DATETIME</code> 的值为 <code>NULL</code>。指定 <code>DATETIME</code> 的值为 <code>NOT NULL</code> 时，如果没有设置默认值，则默认值为 <code>0</code>。</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t1 ( dt1 DATETIME <span class="hljs-keyword">ON</span> <span class="hljs-keyword">UPDATE</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span>, <span class="hljs-comment">-- default NULL</span> dt2 DATETIME <span class="hljs-keyword">NOT</span> <span class="hljs-keyword">NULL</span> <span class="hljs-keyword">ON</span> <span class="hljs-keyword">UPDATE</span> <span class="hljs-built_in">CURRENT_TIMESTAMP</span> <span class="hljs-comment">-- default 0</span> </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><h2 id="时间值的小数部分" style="position:relative">时间值的小数部分<a href="#%E6%97%B6%E9%97%B4%E5%80%BC%E7%9A%84%E5%B0%8F%E6%95%B0%E9%83%A8%E5%88%86" aria-label="时间值的小数部分 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p><code>DATETIME</code> 和 <code>TIMESTAMP</code> 值最多可以有 6 位小数，精确到微秒。如果包含小数部分，值的格式为 <code>YYYY-MM-DD HH:MM:SS[.fraction]</code>，小数部分的范围为 <code>000000</code> 到<code>999999</code>。必须使用小数点分隔小数部分与其他部分。</p><ul><li><p>使用 <code>type_name(fsp)</code> 可以定义精确到小数的列，其中 <code>type_name</code> 可以是<code>TIME</code>、<code>DATETIME</code> 或 <code>TIMESTAMP</code>。例如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> t1 (t <span class="hljs-type">TIME</span>(<span class="hljs-number">3</span>), dt DATETIME(<span class="hljs-number">6</span>)); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><p> <code>fsp</code> 范围是 <code>0</code> 到 <code>6</code>。</p><p> <code>0</code> 表示没有小数部分。如果省略了 <code>fsp</code>，默认为 <code>0</code>。</p></li><li><p>当插入包含小数部分的 <code>TIME</code>、<code>DATETIME</code> 或 <code>TIMESTAMP</code> 时，如果小数部分的位数过少或过多，可能需要进行四舍五入。例如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">CREATE</span> <span class="hljs-keyword">TABLE</span> fractest( c1 <span class="hljs-type">TIME</span>(<span class="hljs-number">2</span>), c2 DATETIME(<span class="hljs-number">2</span>), c3 <span class="hljs-type">TIMESTAMP</span>(<span class="hljs-number">2</span>) ); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">Query OK, <span class="hljs-number">0</span> <span class="hljs-keyword">rows</span> affected (<span class="hljs-number">0.33</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">INSERT</span> <span class="hljs-keyword">INTO</span> fractest <span class="hljs-keyword">VALUES</span> <span class="hljs-operator">&gt;</span> (<span class="hljs-string">'17:51:04.777'</span>, <span class="hljs-string">'2014-09-08 17:51:04.777'</span>, <span class="hljs-string">'2014-09-08 17:51:04.777'</span>); </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">Query OK, <span class="hljs-number">1</span> <span class="hljs-type">row</span> affected (<span class="hljs-number">0.03</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> <span class="hljs-operator">*</span> <span class="hljs-keyword">FROM</span> fractest; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">-------------|------------------------|------------------------+</span> <span class="hljs-operator">|</span> c1 <span class="hljs-operator">|</span> c2 <span class="hljs-operator">|</span> c3 <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------------|------------------------|------------------------+</span> <span class="hljs-operator">|</span> <span class="hljs-number">17</span>:<span class="hljs-number">51</span>:<span class="hljs-number">04.78</span> <span class="hljs-operator">|</span> <span class="hljs-number">2014</span><span class="hljs-number">-09</span><span class="hljs-number">-08</span> <span class="hljs-number">17</span>:<span class="hljs-number">51</span>:<span class="hljs-number">04.78</span> <span class="hljs-operator">|</span> <span class="hljs-number">2014</span><span class="hljs-number">-09</span><span class="hljs-number">-08</span> <span class="hljs-number">17</span>:<span class="hljs-number">51</span>:<span class="hljs-number">04.78</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-------------|------------------------|------------------------+</span> <span class="hljs-number">1</span> <span class="hljs-type">row</span> <span class="hljs-keyword">in</span> <span class="hljs-keyword">set</span> (<span class="hljs-number">0.00</span> sec) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre></li></ul><h2 id="日期和时间类型的转换" style="position:relative">日期和时间类型的转换<a href="#%E6%97%A5%E6%9C%9F%E5%92%8C%E6%97%B6%E9%97%B4%E7%B1%BB%E5%9E%8B%E7%9A%84%E8%BD%AC%E6%8D%A2" aria-label="日期和时间类型的转换 permalink" class="anchor after"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a></h2><p>在日期和时间类型之间进行转换时，有些转换可能会导致信息丢失。例如，<code>DATE</code>、<code>DATETIME</code> 和 <code>TIMESTAMP</code> 都有各自的有效值范围。<code>TIMESTAMP</code> 不能早于 UTC 时间的 1970 年，也不能晚于 UTC 时间的 <code>2038-01-19 03:14:07</code>。根据这个规则，<code>1968-01-01</code> 对于 <code>DATE</code> 或 <code>DATETIME</code> 是有效的，但当 <code>1968-01-01</code> 转换为 <code>TIMESTAMP</code> 时，就会变成 0。</p><p><code>DATE</code> 的转换：</p><ul><li>当 <code>DATE</code> 转换为 <code>DATETIME</code> 或 <code>TIMESTAMP</code> 时，会添加时间部分 <code>00:00:00</code>，因为 <code>DATE</code> 不包含任何时间信息。</li><li>当 <code>DATE</code> 转换为 <code>TIME</code> 时，结果是 <code>00:00:00</code>。</li></ul><p><code>DATETIME</code> 或 <code>TIMESTAMP</code> 的转换：</p><ul><li>当 <code>DATETIME</code> 或 <code>TIMESTAMP</code> 转换为 <code>DATE</code> 时，时间和小数部分将被舍弃。例如，<code>1999-12-31 23:59:59.499</code> 被转换为 <code>1999-12-31</code>。</li><li>当 <code>DATETIME</code> 或 <code>TIMESTAMP</code> 转换为 <code>TIME</code> 时，日期部分被舍弃，因为 <code>TIME</code> 不包含任何日期信息。</li></ul><p>如果要将 <code>TIME</code> 转换为其他时间和日期格式，日期部分会自动指定为 <code>CURRENT_DATE()</code>。最终的转换结果是由 <code>TIME</code> 和 <code>CURRENT_DATE()</code> 组成的日期。也就是说，如果 <code>TIME</code> 的值超出了 <code>00:00:00</code> 到 <code>23:59:59</code> 的范围，那么转换后的日期部分并不表示当前的日期。</p><p>当 <code>TIME</code> 转换为 <code>DATE</code> 时，转换过程类似，时间部分被舍弃。</p><p>使用 <code>CAST()</code> 函数可以显式地将值转换为 <code>DATE</code> 类型。例如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia">date_col <span class="hljs-operator">=</span> <span class="hljs-built_in">CAST</span>(datetime_col <span class="hljs-keyword">AS</span> <span class="hljs-type">DATE</span>) </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><p>将 <code>TIME</code> 和 <code>DATETIME</code> 转换为数字格式。例如：</p><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> CURTIME(), CURTIME()<span class="hljs-operator">+</span><span class="hljs-number">0</span>, CURTIME(<span class="hljs-number">3</span>)<span class="hljs-operator">+</span><span class="hljs-number">0</span>; </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-operator">+</span><span class="hljs-comment">-----------|-------------|--------------+</span> <span class="hljs-operator">|</span> CURTIME() <span class="hljs-operator">|</span> CURTIME()<span class="hljs-operator">+</span><span class="hljs-number">0</span> <span class="hljs-operator">|</span> CURTIME(<span class="hljs-number">3</span>)<span class="hljs-operator">+</span><span class="hljs-number">0</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-----------|-------------|--------------+</span> <span class="hljs-operator">|</span> <span class="hljs-number">09</span>:<span class="hljs-number">28</span>:<span class="hljs-number">00</span> <span class="hljs-operator">|</span> <span class="hljs-number">92800</span> <span class="hljs-operator">|</span> <span class="hljs-number">92800.887</span> <span class="hljs-operator">|</span> <span class="hljs-operator">+</span><span class="hljs-comment">-----------|-------------|--------------+</span> </div><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-1rmx1rm" tabindex="0" type="button" aria-label="Toggle code wrap"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="WrapTextIcon"><path d="M4 19h6v-2H4v2zM20 5H4v2h16V5zm-3 6H4v2h13.25c1.1 0 2 .9 2 2s-.9 2-2 2H15v-2l-3 3 3 3v-2h2c2.21 0 4-1.79 4-4s-1.79-4-4-4z"/></svg></button><button class="MuiButtonBase-root MuiIconButton-root MuiIconButton-sizeSmall css-fxo539" tabindex="0" type="button" aria-label="copy"><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ContentCopyIcon"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg></button></code></pre><pre><code class="hljs language-sql"><div class="MuiBox-root css-1qhimia"><span class="hljs-keyword">SELECT</span> NOW(), NOW()<span class="hljs-operator">+</span><span class="hljs-number">0</span>, NOW(<span class="hljs-number">3</span>)<span class="hljs-operator">+</span><span class="hljs-number">0</span>;