sql中ANY、SOME、ALL关键字
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带any嵌套查询
select emp.empno,emp.ename,emp.sal from scott.emp where sal>any(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal>2975 or sal>2850 or sal>2450
带some嵌套查询
select emp.empno,emp.ename,emp.sal from scott.emp where sal=some(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal=2975 or sal=2850 or sal=2450
注:any与some是等价的
带all嵌套查询
select emp.empno,emp.ename,emp.sal from scott.emp where sal>all(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal>2975 and sal>2850 and sal>2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal>any(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal>2975 or sal>2850 or sal>2450
带some嵌套查询
select emp.empno,emp.ename,emp.sal from scott.emp where sal=some(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal=2975 or sal=2850 or sal=2450
注:any与some是等价的
带all嵌套查询
select emp.empno,emp.ename,emp.sal from scott.emp where sal>all(select sal from scott.emp where job='manager');
等价于
select sal from scott.emp where job='manager' 结果为 sal:2975 2850 2450
select emp.empno,emp.ename,emp.sal from scott.emp where sal>2975 and sal>2850 and sal>2450
ALL与ANY的关系就是,AND 与 OR 的关系。 ANY与SOME等价,据说搞这两个不同的词出来是为了迁就英语语法。例如,在用= ANY 的地方在(英语)语法上就应该是= SOME。 IN 与 = ANY 等价,均表示,变量在(子查询)列表之中,即 a IN (table B) 表示 a = ANY B.b NOT IN 与 <> ALL 等价,而不等于<> ANY,前两者均表示,变量不在(子查询)列表之中,即 a NOT IN (table B) 表示 a <> ALL B.b。而如果a <> ANY B.b,则只要任意一个b<>a就true了。 IN 与 EXISTS 的性能区别主要来自,IN 会编列子查询的每行记录,然后再返回,而EXISTS 则只要遇到第一个满足条件的记录就马上返回。 NOT IN 与 NOT EXISTS 并不能完全等价,只有当子查询中,select 关键字后的字段有not null约束或者有这种暗示时才用NOT IN。
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