在SQL*Plus脚本中声明变量有多种方法。

第一种方法是使用VAR声明绑定变量。为VAR分配值的机制是使用EXEC调用：

SQL> var name varchar2(20)
SQL> exec :name := 'SALES'
PL/SQL procedure successfully completed.
SQL> select * from dept
  2  where dname = :name
    DEPTNO DNAME          LOC
---------- -------------- -------------
        30 SALES          CHICAGO
SQL>

当我们想要调用具有OUT参数或函数的存储过程时，VAR特别有用。

或者，我们可以使用替代变量。这些对于交互模式是很好的：

SQL> accept p_dno prompt "Please enter Department number: " default 10
Please enter Department number: 20
SQL> select ename, sal
  2  from emp
  3  where deptno = &p_dno
old   3: where deptno = &p_dno
new   3: where deptno = 20
ENAME             SAL
---------- ----------
CLARKE            800
ROBERTSON        2975
RIGBY            3000
KULASH           1100
GASPAROTTO       3000
SQL>

当我们编写一个调用其他脚本的脚本时，预先对变量进行DEFine是很有用的。此代码段运行时不会提示我输入值：

SQL> def p_dno = 40
SQL> select ename, sal
  2  from emp
  3  where deptno = &p_dno
old   3: where deptno = &p_dno
new   3: where deptno = 40
no rows selected
SQL>

最后是匿名PL/SQL块。如您所见，我们仍然可以交互地为声明的变量赋值：

SQL> set serveroutput on size unlimited
SQL> declare
  2      n pls_integer;
  3      l_sal number := 3500;
  4      l_dno number := &dno;
  5  begin
  6      select count(*)
  7      into n
  8      from emp
  9      where sal > l_sal
 10      and deptno = l_dno;
 11      dbms_output.put_line('top earners = '||to_char(n));
 12  end;
 13  /
Enter value for dno: 10
old   4:     l_dno number := &dno;
new   4:     l_dno number := 10;
top earners = 1
PL/SQL procedure successfully completed.
SQL>

如果是char变量，请尝试使用双引号：

DEFINE stupidvar = "'stupidvarcontent'";

或

DEFINE stupidvar = 'stupidvarcontent';
SELECT stupiddata  
FROM stupidtable  
WHERE stupidcolumn = '&stupidvar'

更新：

SQL*Plus: Release 10.2.0.1.0 - Production on Wed Aug 25 17:13:26 2010
SQL> conn od/od@etalon
Connected.
SQL> define var = "'FL-208'";
SQL> select code from product where code = &var;
old   1: select code from product where code = &var
new   1: select code from product where code = 'FL-208'
---------------
FL-208
SQL> define var = 'FL-208';
SQL> select code from product where code = &var;
old   1: select code from product where code = &var
new   1: select code from product where code = FL-208
select code from product where code = FL-208
ERROR at line 1:
ORA-06553: PLS-221: 'FL' is not a procedure or is undefined

在PL/SQL v.10中

关键字declare用于声明变量

DECLARE stupidvar varchar(20);

要赋值，可以在声明时设置该值

DECLARE stupidvar varchar(20) := '12345678';

或者，要选择某个变量中的内容，您可以使用 INTO 语句，但是您需要在 BEGIN 和 END 中包装语句，还需要确保只返回单个值，并且不要忘记使用分号。

因此，完整的声明如下：

DECLARE stupidvar varchar(20);
BEGIN
    SELECT stupid into stupidvar FROM stupiddata CC 
    WHERE stupidid = 2;
END;

您的变量只能在 BEGIN 和 END 中使用，因此如果您想使用多个变量，则必须执行多个 BEGIN END 包装

DECLARE stupidvar varchar(20);
BEGIN
    SELECT stupid into stupidvar FROM stupiddata CC 
    WHERE stupidid = 2;
    DECLARE evenmorestupidvar varchar(20);
    BEGIN
        SELECT evenmorestupid into evenmorestupidvar FROM evenmorestupiddata CCC 
        WHERE evenmorestupidid = 42;