搜索条件中使用的子查询

子查询需要用作搜索条件才能过滤结果。它们指定了从包含查询的 select-list、查询表达式或子查询自身返回行的条件。此操作评估为 TRUE、FALSE 或 UNKNOWN (NULL)。

语法

search‑condition {
    [ { AND | OR | NOT } {  predicate | ( search‑condition ) } ]
   }[,... ]
 predicate
     { expression comparison‑operator expression
         | string‑expression [ NOT ] { LIKE | ILIKE | LIKEB | ILIKEB } string-expression
         | expression IS [ NOT ] NULL
         | expression [ NOT ] IN ( subquery | expression[,... ] )
         | expression comparison‑operator [ ANY | SOME ] ( subquery )
         | expression comparison‑operator ALL ( subquery )
         | expression OR ( subquery )
         | [ NOT ] EXISTS ( subquery )
         | [ NOT ] IN ( subquery )
     }

参数