Type Conversion Functions

Common Issues with Data Conversion ​

ClickHouse generally uses the same behavior as C++ programs .

to<type> functions and cast behave differently in some cases, for example in case of LowCardinality : cast removes LowCardinality trait to<type> functions don't. The same with Nullable , this behaviour is not compatible with SQL standard, and it can be changed using cast_keep_nullable setting.

Example:

SELECT
    toTypeName(toLowCardinality('') AS val) AS source_type,
    toTypeName(toString(val)) AS to_type_result_type,
    toTypeName(CAST(val, 'String')) AS cast_result_type

┌─source_type────────────┬─to_type_result_type────┬─cast_result_type─┐
│ LowCardinality(String) │ LowCardinality(String) │ String           │
└────────────────────────┴────────────────────────┴──────────────────┘

SELECT
    toTypeName(toNullable('') AS val) AS source_type,
    toTypeName(toString(val)) AS to_type_result_type,
    toTypeName(CAST(val, 'String')) AS cast_result_type

┌─source_type──────┬─to_type_result_type─┬─cast_result_type─┐
│ Nullable(String) │ Nullable(




    
String)    │ String           │
└──────────────────┴─────────────────────┴──────────────────┘

SELECT
    toTypeName(toNullable('') AS val) AS source_type,
    toTypeName(toString(val)) AS to_type_result_type,
    toTypeName(CAST(val, 'String')) AS cast_result_type
SETTINGS cast_keep_nullable = 1

┌─source_type──────┬─to_type_result_type─┬─cast_result_type─┐
│ Nullable(String) │ Nullable(String)    │ Nullable(String) │
└──────────────────┴─────────────────────┴──────────────────┘

toInt(8 | 16 | 32 | 64 | 128 | 256) ​

Converts an input value to a value the Int data type. This function family includes:

• toInt8(expr) — Converts to a value of data type Int8 .
• toInt16(expr) — Converts to a value of data type Int16 .
• toInt32(expr) — Converts to a value of data type Int32 .
• toInt64(expr) — Converts to a value of data type Int64 .
• toInt128(expr) — Converts to a value of data type Int128 .
• toInt256(expr) — Converts to a value of data type Int256 .

Arguments

• expr — Expression returning a number or a string with the decimal representation of a number. Binary, octal, and hexadecimal representations of numbers are not supported. Leading zeroes are stripped.

Returned value

Integer value in the Int8 , Int16 , Int32 , Int64 , Int128 or Int256 data type.

Functions use rounding towards zero , meaning they truncate fractional digits of numbers.

The behavior of functions for the NaN and Inf arguments is undefined. Remember about numeric conversions issues , when using the functions.

Example

Query:

SELECT toInt64(nan), toInt32(32), toInt16('16'), toInt8(8.8);

Result:

┌─────────toInt64(nan)─┬─toInt32(32)─┬─toInt16('16')─┬─toInt8(8.8)─┐
│ -9223372036854775808 │          32 │            16 │           8 │
└──────────────────────┴─────────────┴───────────────┴─────────────┘

toInt(8 | 16 | 32 | 64 | 128 | 256)OrZero ​

Takes an argument of type String and tries to parse it into an Int (8 | 16 | 32 | 64 | 128 | 256). If unsuccessful, returns 0 .

Example

Query:

SELECT toInt64OrZero('123123'), toInt8OrZero('123qwe123');

Result:

┌─toInt64OrZero('123123')─┬─toInt8OrZero('123qwe123')─┐
│                  123123 │                         0 │
└─────────────────────────┴───────────────────────────┘

toInt(8 | 16 | 32 | 64 | 128 | 256)OrNull ​

It takes an argument of type String and tries to parse it into Int (8 | 16 | 32 | 64 | 128 | 256). If unsuccessful, returns NULL .

Example

Query:

SELECT toInt64OrNull('123123'), toInt8OrNull('123qwe123');

Result:

┌─toInt64OrNull('123123')─┬─toInt8OrNull('123qwe123')─┐
│                  123123 │                      ᴺᵁᴸᴸ │
└─────────────────────────┴───────────────────────────┘

toInt(8 | 16 | 32 | 64 | 128 | 256)OrDefault ​

It takes an argument of type String and tries to parse it into Int (8 | 16 | 32 | 64 | 128 | 256). If unsuccessful, returns the default type value.

Example

Query:

SELECT toInt64OrDefault('123123', cast('-1' as Int64)), toInt8OrDefault('123qwe123', cast('-1' as Int8));

Result:

┌─toInt64OrDefault('123123', CAST('-1', 'Int64'))─┬─toInt8OrDefault('123qwe123', CAST('-1', 'Int8'))─┐
│                                          123123 │                                               -1 │
└─────────────────────────────────────────────────┴──────────────────────────────────────────────────┘

toUInt(8 | 16 | 32 | 64 | 256) ​

Converts an input value to the UInt data type. This function family includes:

• toUInt8(expr) — Converts to a value of data type UInt8 .
• toUInt16(expr) — Converts to a value of data type UInt16 .
• toUInt32(expr) — Converts to a value of data type UInt32 .
• toUInt64(expr) — Converts to a value of data type UInt64 .
• toUInt256(expr) — Converts to a value of data type UInt256 .

Arguments

• expr — Expression returning a number or a string with the decimal representation of a number. Binary, octal, and hexadecimal representations of numbers are not supported. Leading zeroes are stripped.

Returned value

• Integer value in the UInt8 , UInt16 , UInt32 , UInt64 or UInt256 data type.

Functions use rounding towards zero , meaning they truncate fractional digits of numbers.

The behavior of functions for negative arguments and for the NaN and Inf arguments is undefined. If you pass a string with a negative number, for example '-32' , ClickHouse raises an exception. Remember about numeric conversions issues , when using the functions.

Example

Query:

SELECT toUInt64(nan), toUInt32(-32), toUInt16('16'), toUInt8(8.8);

Result:

┌───────toUInt64(nan)─┬─toUInt32(-32)─┬─toUInt16('16')─┬─toUInt8(8.8)─┐
│ 9223372036854775808 │    4294967264 │             16 │            8 │
└─────────────────────┴───────────────┴────────────────┴──────────────┘

toUInt(8 | 16 | 32 | 64 | 256)OrZero ​

toUInt(8 | 16 | 32 | 64 | 256)OrNull ​

toUInt(8 | 16 | 32 | 64 | 256)OrDefault ​

toFloat(32 | 64) ​

toFloat(32 | 64)OrZero ​

toFloat(32 | 64)OrNull ​

toFloat(32 | 64)OrDefault ​

toDate ​

Converts the argument to Date data type.

If the argument is DateTime or DateTime64 , it truncates it and leaves the date component of the DateTime:

SELECT
    now() AS x,
    toDate(x)

┌───────────────────x─┬─toDate(now())─┐
│ 2022-12-30 13:44:17 │    2022-12-30 │
└─────────────────────┴───────────────┘

If the argument is a String , it is parsed as Date or DateTime . If it was parsed as DateTime , the date component is being used:

SELECT
    toDate('2022-12-30') AS x,
    toTypeName(x)

┌──────────x─┬─toTypeName(toDate('2022-12-30'))─┐
│ 2022-12-30 │ Date                             │
└────────────┴──────────────────────────────────┘

1 row in set. Elapsed: 0.001 sec.

SELECT
    toDate('2022-12-30 01:02:03') AS x,
    toTypeName(x)

┌──────────x─┬─toTypeName(toDate('2022-12-30 01:02:03'))─┐
│ 2022-12-30 │ Date                                      │
└────────────┴───────────────────────────────────────────┘

If the argument is a number and looks like a UNIX timestamp (is greater than 65535), it is interpreted as a DateTime , then truncated to Date in the current timezone. The timezone argument can be specified as a second argument of the function. The truncation to Date depends on the timezone:

SELECT
    now() AS current_time,
    toUnixTimestamp(current_time) AS ts,
    toDateTime(ts) AS time_Amsterdam,
    toDateTime(ts, 'Pacific/Apia') AS time_Samoa,
    toDate(time_Amsterdam) AS date_Amsterdam,
    toDate(time_Samoa) AS date_Samoa,
    toDate(ts)




    
 AS date_Amsterdam_2,
    toDate(ts, 'Pacific/Apia') AS date_Samoa_2

Row 1:
──────
current_time:     2022-12-30 13:51:54
ts:               1672404714
time_Amsterdam:   2022-12-30 13:51:54
time_Samoa:       2022-12-31 01:51:54
date_Amsterdam:   2022-12-30
date_Samoa:       2022-12-31
date_Amsterdam_2: 2022-12-30
date_Samoa_2:     2022-12-31

The example above demonstrates how the same UNIX timestamp can be interpreted as different dates in different time zones.

If the argument is a number and it is smaller than 65536, it is interpreted as the number of days since 1970-01-01 (the first UNIX day) and converted to Date . It corresponds to the internal numeric representation of the Date data type. Example:

SELECT toDate(12345)

┌─toDate(12345)─┐
│    2003-10-20 │
└───────────────┘

This conversion does not depend on timezones.

If the argument does not fit in the range of the Date type, it results in an implementation-defined behavior, that can saturate to the maximum supported date or overflow:

SELECT toDate(10000000000.)

┌─toDate(10000000000.)─┐
│           2106-02-07 │
└──────────────────────┘

The function toDate can be also written in alternative forms:

SELECT
    now() AS time,
    toDate(time),
    DATE(time),
    CAST(time, 'Date')

┌────────────────time─┬─toDate(now())─┬─DATE(now())─┬─CAST(now(), 'Date')─┐
│ 2022-12-30 13:54:58 │    2022-12-30 │  2022-12-30 │          2022-12-30 │
└─────────────────────┴───────────────┴─────────────┴─────────────────────┘

toDateOrZero ​

The same as toDate but returns lower boundary of Date if an invalid argument is received. Only String argument is supported.

Example

Query:

SELECT toDateOrZero('2022-12-30'), toDateOrZero('');

Result:

┌─toDateOrZero('2022-12-30')─┬─toDateOrZero('')─┐
│                 2022-12-30 │       1970-01-01 │
└────────────────────────────┴──────────────────┘

toDateOrNull ​

The same as toDate but returns NULL if an invalid argument is received. Only String argument is supported.

Example

Query:

SELECT toDateOrNull('2022-12-30'), toDateOrNull('');

Result:

┌─toDateOrNull('2022-12-30')─┬─toDateOrNull('')─┐
│                 2022-12-30 │             ᴺᵁᴸᴸ │
└────────────────────────────┴──────────────────┘

toDateOrDefault ​

Like toDate but if unsuccessful, returns a default value which is either the second argument (if specified), or otherwise the lower boundary of Date .

Syntax

toDateOrDefault(expr [, default_value])

Example

Query:

SELECT toDateOrDefault('2022-12-30'), toDateOrDefault('', '2023-01-01'::Date);

Result:

┌─toDateOrDefault('2022-12-30')─┬─toDateOrDefault('', CAST('2023-01-01', 'Date'))─┐
│                    2022-12-30 │                                      2023-01-01 │
└───────────────────────────────┴─────────────────────────────────────────────────┘

toDateTime ​

Converts an input value to DateTime .

Syntax

toDateTime(expr[, time_zone ])

Arguments

• expr — The value. String , Int , Date or DateTime .
• time_zone — Time zone. String .

Returned value

• A date time. DateTime

Example

Query:

SELECT toDateTime('2022-12-30 13:44:17'), toDateTime(1685457500, 'UTC');

Result:

┌─toDateTime('2022-12-30 13:44:17')─┬─toDateTime(1685457500, 'UTC')─┐
│               2022-12-30 13:44:17 │           2023-05-30 14:38:20 │




    

└───────────────────────────────────┴───────────────────────────────┘

toDateTimeOrZero ​

The same as toDateTime but returns lower boundary of DateTime if an invalid argument is received. Only String argument is supported.

Example

Query:

SELECT toDateTimeOrZero('2022-12-30 13:44:17'), toDateTimeOrZero('');

Result:

┌─toDateTimeOrZero('2022-12-30 13:44:17')─┬─toDateTimeOrZero('')─┐
│                     2022-12-30 13:44:17 │  1970-01-01 00:00:00 │
└─────────────────────────────────────────┴──────────────────────┘

toDateTimeOrNull ​

The same as toDateTime but returns NULL if an invalid argument is received. Only String argument is supported.

Example

Query:

SELECT toDateTimeOrNull('2022-12-30 13:44:17'), toDateTimeOrNull('');

Result:

┌─toDateTimeOrNull('2022-12-30 13:44:17')─┬─toDateTimeOrNull('')─┐
│                     2022-12-30 13:44:17 │                 ᴺᵁᴸᴸ │
└─────────────────────────────────────────┴──────────────────────┘

toDateTimeOrDefault ​

Like toDateTime but if unsuccessful, returns a default value which is either the third argument (if specified), or otherwise the lower boundary of DateTime .

Syntax

toDateTimeOrDefault(expr [, time_zone [, default_value]])

Example

Query:

SELECT toDateTimeOrDefault('2022-12-30 13:44:17'), toDateTimeOrDefault('', 'UTC', '2023-01-01'::DateTime('UTC'));

Result:

┌─toDateTimeOrDefault('2022-12-30 13:44:17')─┬─toDateTimeOrDefault('', 'UTC', CAST('2023-01-01', 'DateTime(\'UTC\')'))─┐
│                        2022-12-30 13:44:17 │                                                     2023-01-01 00:00:00 │
└────────────────────────────────────────────┴─────────────────────────────────────────────────────────────────────────┘

toDate32 ​

Converts the argument to the Date32 data type. If the value is outside the range, toDate32 returns the border values supported by Date32 . If the argument has Date type, it's borders are taken into account.

Syntax

toDate32(expr)

Arguments

• expr — The value. String , UInt32 or Date .

Returned value

• A calendar date. Type Date32 .

Example

1. The value is within the range:

SELECT toDate32('1955-01-01') AS value, toTypeName(value);

┌──────value─┬─toTypeName(toDate32('1925-01-01'))─┐
│ 1955-01-01 │ Date32                             │
└────────────┴────────────────────────────────────┘

2. The value is outside the range:

SELECT toDate32('1899-01-01') AS value, toTypeName(value);

┌──────value─┬─toTypeName(toDate32('1899-01-01'))─┐
│ 1900-01-01 │ Date32                             │
└────────────┴────────────────────────────────────┘

3. With Date argument:

SELECT toDate32(toDate('1899-01-01')) AS value, toTypeName(value);

┌──────value─┬─toTypeName(toDate32(toDate('1899-01-01')))─┐
│ 1970-01-01 │ Date32                                     │
└────────────┴────────────────────────────────────────────┘

toDate32OrZero ​

The same as toDate32 but returns the min value of Date32 if an invalid argument is received.

Example

Query:

SELECT toDate32OrZero('1899-01-01'), toDate32OrZero('');

Result:

┌─toDate32OrZero('1899-01-01')─┬─toDate32OrZero('')─┐
│                   1900-01-01 │         1900-01-01 │
└──────────────────────────────┴────────────────────┘

toDate32OrNull ​

The same as toDate32 but returns NULL if an invalid argument is received.

Example

Query:

SELECT toDate32OrNull('1955-01-01'), toDate32OrNull('');

Result:

┌─toDate32OrNull('1955-01-01')─┬─toDate32OrNull('')─┐




    

│                   1955-01-01 │               ᴺᵁᴸᴸ │
└──────────────────────────────┴────────────────────┘

toDate32OrDefault ​

Converts the argument to the Date32 data type. If the value is outside the range, toDate32OrDefault returns the lower border value supported by Date32 . If the argument has Date type, it's borders are taken into account. Returns default value if an invalid argument is received.

Example

Query:

SELECT
    toDate32OrDefault('1930-01-01', toDate32('2020-01-01')),
    toDate32OrDefault('xx1930-01-01', toDate32('2020-01-01'));

Result:

┌─toDate32OrDefault('1930-01-01', toDate32('2020-01-01'))─┬─toDate32OrDefault('xx1930-01-01', toDate32('2020-01-01'))─┐
│                                              1930-01-01 │                                                2020-01-01 │
└─────────────────────────────────────────────────────────┴───────────────────────────────────────────────────────────┘

toDateTime64 ​

Converts the argument to the DateTime64 data type.

Syntax

toDateTime64(expr, scale, [timezone])

Arguments

• expr — The value. String , UInt32 , Float or DateTime .
• scale - Tick size (precision): 10 ^-precision seconds. Valid range: [ 0 : 9 ] .
• timezone - Time zone of the specified datetime64 object.

Returned value

• A calendar date and time of day, with sub-second precision.

Type: DateTime64 .

Example

1. The value is within the range:

SELECT toDateTime64('1955-01-01 00:00:00.000', 3) AS value, toTypeName(value);

┌───────────────────value─┬─toTypeName(toDateTime64('1955-01-01 00:00:00.000', 3))─┐
│ 1955-01-01 00:00:00.000 │ DateTime64(3)                                          │
└─────────────────────────┴────────────────────────────────────────────────────────┘

2. As decimal with precision:

SELECT toDateTime64(1546300800.000, 3) AS value, toTypeName(value);

┌───────────────────value─┬─toTypeName(toDateTime64(1546300800., 3))─┐
│ 2019-01-01 00:00:00.000 │ DateTime64(3)                            │
└─────────────────────────┴──────────────────────────────────────────┘

Without the decimal point the value is still treated as Unix Timestamp in seconds:

SELECT toDateTime64(




    
1546300800000, 3) AS value, toTypeName(value);

┌───────────────────value─┬─toTypeName(toDateTime64(1546300800000, 3))─┐
│ 2282-12-31 00:00:00.000 │ DateTime64(3)                              │
└─────────────────────────┴────────────────────────────────────────────┘

3. With timezone :

SELECT toDateTime64('2019-01-01 00:00:00', 3, 'Asia/Istanbul') AS value, toTypeName(value);

┌───────────────────value─┬─toTypeName(toDateTime64('2019-01-01 00:00:00', 3, 'Asia/Istanbul'))─┐
│ 2019-01-01 00:00:00.000 │ DateTime64(3, 'Asia/Istanbul')                                      │
└─────────────────────────┴─────────────────────────────────────────────────────────────────────┘

toDateTime64OrZero ​

toDateTime64OrNull ​

toDateTime64OrDefault ​

toDecimal(32 | 64 | 128 | 256) ​

Converts value to the Decimal data type with precision of S . The value can be a number or a string. The S (scale) parameter specifies the number of decimal places.

• toDecimal32(value, S)
• toDecimal64(value, S)
• toDecimal128(value, S)
• toDecimal256(value, S)

toDecimal(32 | 64 | 128 | 256)OrNull ​

Converts an input string to a Nullable(Decimal(P,S)) data type value. This family of functions includes:

• toDecimal32OrNull(expr, S) — Results in Nullable(Decimal32(S)) data type.
• toDecimal64OrNull(expr, S) — Results in Nullable(Decimal64(S)) data type.
• toDecimal128OrNull(expr, S) — Results in Nullable(Decimal128(S)) data type.
• toDecimal256OrNull(expr, S) — Results in Nullable(Decimal256(S)) data type.

These functions should be used instead of toDecimal*() functions, if you prefer to get a NULL value instead of an exception in the event of an input value parsing error.

Arguments

• expr — Expression , returns a value in the String data type. ClickHouse expects the textual representation of the decimal number. For example, '1.111' .
• S — Scale, the number of decimal places in the resulting value.

Returned value

A value in the Nullable(Decimal(P,S)) data type. The value contains:

• Number with S decimal places, if ClickHouse interprets the input string as a number.
• NULL , if ClickHouse can’t interpret the input string as a number or if the input number contains more than S decimal places.

Examples

Query:

SELECT toDecimal32OrNull(toString(-1.111), 5) AS val, toTypeName(val);

Result:

┌────val─┬─toTypeName(toDecimal32OrNull(toString(-1.111), 5))─┐
│ -1.111 │ Nullable(Decimal(9, 5))                            │
└────────┴────────────────────────────────────────────────────┘

Query:

SELECT toDecimal32OrNull(toString(-1.111), 2) AS val, toTypeName(




    
val);

Result:

┌──val─┬─toTypeName(toDecimal32OrNull(toString(-1.111), 2))─┐
│ ᴺᵁᴸᴸ │ Nullable(Decimal(9, 2))                            │
└──────┴────────────────────────────────────────────────────┘

toDecimal(32 | 64 | 128 | 256)OrDefault ​

Converts an input string to a Decimal(P,S) data type value. This family of functions includes:

• toDecimal32OrDefault(expr, S) — Results in Decimal32(S) data type.
• toDecimal64OrDefault(expr, S) — Results in Decimal64(S) data type.
• toDecimal128OrDefault(expr, S) — Results in Decimal128(S) data type.
• toDecimal256OrDefault(expr, S) — Results in Decimal256(S) data type.

These functions should be used instead of toDecimal*() functions, if you prefer to get a default value instead of an exception in the event of an input value parsing error.

Arguments

• expr — Expression , returns a value in the String data type. ClickHouse expects the textual representation of the decimal number. For example, '1.111' .
• S — Scale, the number of decimal places in the resulting value.

Returned value

A value in the Decimal(P,S) data type. The value contains:

• Number with S decimal places, if ClickHouse interprets the input string as a number.
• Default Decimal(P,S) data type value, if ClickHouse can’t interpret the input string as a number or if the input number contains more than S decimal places.

Examples

Query:

SELECT toDecimal32OrDefault(toString(-1.111), 5) AS val, toTypeName(val);

Result:

┌────val─┬─toTypeName(toDecimal32OrDefault(toString(-1.111), 5))─┐
│ -1.111 │ Decimal(9, 5)                                         │
└────────┴───────────────────────────────────────────────────────┘

Query:

SELECT toDecimal32OrDefault(toString(-1.111), 2) AS val, toTypeName(val);

Result:

┌─val─┬─toTypeName(toDecimal32OrDefault(toString(-1.111), 2))─┐
│   0 │ Decimal(9, 2)                                         │
└─────┴───────────────────────────────────────────────────────┘

toDecimal(32 | 64 | 128 | 256)OrZero ​

Converts an input value to the Decimal(P,S) data type. This family of functions includes:

• toDecimal32OrZero( expr, S) — Results in Decimal32(S) data type.
• toDecimal64OrZero( expr, S) — Results in Decimal64(S) data type.
• toDecimal128OrZero( expr, S) — Results in Decimal128(S) data type.
• toDecimal256OrZero( expr, S) — Results in Decimal256(S) data type.

These functions should be used instead of toDecimal*() functions, if you prefer to get a 0 value instead of an exception in the event of an input value parsing error.

Arguments

• expr — Expression , returns a value in the String data type. ClickHouse expects the textual representation of the decimal number. For example, '1.111' .
• S — Scale, the number of decimal places in the resulting value.

Returned value

A value in the Nullable(Decimal(P,S)) data type. The value contains:

• Number with S decimal places, if ClickHouse interprets the input string as a number.
• 0 with S decimal places, if ClickHouse can’t interpret the input string as a number or if the input number contains more than S decimal places.

Example

Query:

SELECT toDecimal32OrZero(toString(-1.111), 5) AS




    
 val, toTypeName(val);

Result:

┌────val─┬─toTypeName(toDecimal32OrZero(toString(-1.111), 5))─┐
│ -1.111 │ Decimal(9, 5)                                      │
└────────┴────────────────────────────────────────────────────┘

Query:

SELECT toDecimal32OrZero(toString(-1.111), 2) AS val, toTypeName(val);

Result:

┌──val─┬─toTypeName(toDecimal32OrZero(toString(-1.111), 2))─┐
│ 0.00 │ Decimal(9, 2)                                      │
└──────┴────────────────────────────────────────────────────┘

toString ​

Functions for converting between numbers, strings (but not fixed strings), dates, and dates with times. All these functions accept one argument.

When converting to or from a string, the value is formatted or parsed using the same rules as for the TabSeparated format (and almost all other text formats). If the string can’t be parsed, an exception is thrown and the request is canceled.

When converting dates to numbers or vice versa, the date corresponds to the number of days since the beginning of the Unix epoch. When converting dates with times to numbers or vice versa, the date with time corresponds to the number of seconds since the beginning of the Unix epoch.

The date and date-with-time formats for the toDate/toDateTime functions are defined as follows:

YYYY-MM-DD
YYYY-MM-DD hh:mm:ss

As an exception, if converting from UInt32, Int32, UInt64, or Int64 numeric types to Date, and if the number is greater than or equal to 65536, the number is interpreted as a Unix timestamp (and not as the number of days) and is rounded to the date. This allows support for the common occurrence of writing toDate(unix_timestamp) , which otherwise would be an error and would require writing the more cumbersome toDate(toDateTime(unix_timestamp)) .

Conversion between a date and a date with time is performed the natural way: by adding a null time or dropping the time.

Conversion between numeric types uses the same rules as assignments between different numeric types in C++.

Additionally, the toString function of the DateTime argument can take a second String argument containing the name of the time zone. Example: Asia/Yekaterinburg In this case, the time is formatted according to the specified time zone.

Example

Query:

SELECT
    now() AS now_local,
    toString(now(), 'Asia/Yekaterinburg') AS now_yekat;

Result:

┌───────────now_local─┬─now_yekat───────────┐
│ 2016-06-15 00:11:21 │ 2016-06-15 02:11:21 │
└─────────────────────┴─────────────────────┘

Also see the toUnixTimestamp function.

toFixedString(s, N) ​

Converts a String type argument to a FixedString(N) type (a string of fixed length N). If the string has fewer bytes than N, it is padded with null bytes to the right. If the string has more bytes than N, an exception is thrown.

toStringCutToZero(s) ​

Accepts a String or FixedString argument. Returns the String with the content truncated at the first zero byte found.

Example

Query:

SELECT toFixedString('foo', 8) AS s, toStringCutToZero(s) AS s_cut;

Result:

┌─s─────────────┬─s_cut─┐
│ foo\0\0\0\0\0 │ foo   │




    

└───────────────┴───────┘

Query:

SELECT toFixedString('foo\0bar', 8) AS s, toStringCutToZero(s) AS s_cut;

Result:

┌─s──────────┬─s_cut─┐
│ foo\0bar\0 │ foo   │
└────────────┴───────┘

toDecimalString ​

Converts a numeric value to String with the number of fractional digits in the output specified by the user.

Syntax

toDecimalString(number, scale)

Parameters

• number — Value to be represented as String, Int, UInt , Float , Decimal ,
• scale — Number of fractional digits, UInt8 .
  • Maximum scale for Decimal and Int, UInt types is 77 (it is the maximum possible number of significant digits for Decimal),
  • Maximum scale for Float is 60.

Returned value

• Input value represented as String with given number of fractional digits (scale). The number is rounded up or down according to common arithmetic in case requested scale is smaller than original number's scale.

Example

Query:

SELECT toDecimalString(CAST('64.32', 'Float64'), 5);

Result:

┌toDecimalString(CAST('64.32', 'Float64'), 5)─┐
│ 64.32000                                    │
└─────────────────────────────────────────────┘

reinterpretAsUInt(8 | 16 | 32 | 64) ​

reinterpretAsInt(8 | 16 | 32 | 64) ​

reinterpretAsFloat(32 | 64) ​

reinterpretAsDate ​

reinterpretAsDateTime ​

These functions accept a string and interpret the bytes placed at the beginning of the string as a number in host order (little endian). If the string isn’t long enough, the functions work as if the string is padded with the necessary number of null bytes. If the string is longer than needed, the extra bytes are ignored. A date is interpreted as the number of days since the beginning of the Unix Epoch, and a date with time is interpreted as the number of seconds since the beginning of the Unix Epoch.

reinterpretAsString ​

This function accepts a number or date or date with time and returns a string containing bytes representing the corresponding value in host order (little endian). Null bytes are dropped from the end. For example, a UInt32 type value of 255 is a string that is one byte long.

reinterpretAsFixedString ​

This function accepts a number or date or date with time and returns a FixedString containing bytes representing the corresponding value in host order (little endian). Null bytes are dropped from the end. For example, a UInt32 type value of 255 is a FixedString that is one byte long.

reinterpretAsUUID ​

Accepts 16 bytes string and returns UUID containing bytes representing the corresponding value in network byte order (big-endian). If the string isn't long enough, the function works as if the string is padded with the necessary number of null bytes to the end. If the string is longer than 16 bytes, the extra bytes at the end are ignored.

Syntax

reinterpretAsUUID(fixed_string)

Arguments

• fixed_string — Big-endian byte string. FixedString .

Returned value

• The UUID type value. UUID .

Examples

String to UUID.

Query:

SELECT reinterpretAsUUID(reverse(unhex('000102030405060708090a0b0c0d0e0f')));

Result:

┌─reinterpretAsUUID(reverse(unhex('000102030405060708090a0b0c0d0e0f')))─┐
│                                  08090a0b-0c0d-0e0f-0001-020304050607 │
└───────────────────────────────────────────────────────────────────────┘

Going back and forth from String to UUID.

Query:

WITH
    generateUUIDv4() AS uuid,
    identity(lower(hex(reverse(reinterpretAsString(uuid))))) AS str,
    reinterpretAsUUID(reverse(unhex(str))) AS uuid2
SELECT uuid = uuid2;

Result:

┌─equals(uuid, uuid2)─┐
│                   1 │
└─────────────────────┘

reinterpret(x, T) ​

Uses the same source in-memory bytes sequence for x value and reinterprets it to destination type.

Syntax

reinterpret(x, type)

Arguments

• x — Any type.
• type — Destination type. String .

Returned value

• Destination type value.

Examples

Query:

SELECT reinterpret(toInt8(-1), 'UInt8') as int_to_uint,
    reinterpret(toInt8(1), 'Float32') as int_to_float,
    reinterpret('1', 'UInt32') as string_to_int;

Result:

┌─int_to_uint─┬─int_to_float─┬─string_to_int─┐
│         255 │        1e-45 │            49 │
└─────────────┴──────────────┴───────────────┘

CAST(x, T) ​

Converts an input value to the specified data type. Unlike the reinterpret function, CAST tries to present the same value using the new data type. If the conversion can not be done then an exception is raised.