Question

SQL中SELECT中的FROM子句可否带另外一个SELECT

关系运算的结果也是关系,那么这样的句子对不对?
SELECT *
FROM (SELECT ... )
WHERE ...
也就是说把FROM后面的SELECT子句的运算结果当作一个表来用.

Answer 1

方式很多
你写的这个是子查询的一种
SELECT ...
FROM (SELECT ... )
WHERE ...

SELECT ...
FROM ...
WHERE ...=(SELECT ... )

SELECT ...(SELECT ... )
FROM ...
WHERE ...