探讨"INNER JOIN (SELECT * FROM A)"与"INNER JOIN A"的区别
布谷歌 2008-09-09 05:00:31 SELECT 列字段
INTO #SALINFO
FROM DeptAll('1', @USEYN) A
INNER JOIN
(
SELECT * FROM
(
SELECT DISTINCT TOP 100 PERCENT 列字段
FROM
(SELECT * FROM @TBLGOAL) B
INNER JOIN COMDB..CODE_H C1 ON ...
INNER JOIN COMDB..CODE_H C2 ON ...
GROUP BY 列字段
) S
) S ON ...
就这个sql语句,大家帮忙看下(SELECT * FROM @TBLGOAL)有什么作用?为什么不直接用@TBLGOAL?
同样的还有inner join select* from S 为什么不直接inner join S 呢?
当然,我知道它们的结果是一样的.但是还有什么区别呢?