关于子查询中不能使用order by 的理解

select * from (select * from emp e where e.sal < 1000 order by e.empno) t order by t.sal desc; 这条SQL的子查询里面 包含了子查询 就能够执行 而下面这条SQL [quote]select * from emp where dept in (select dept from valid_deps whe

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