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数据库环境:SQL SERVER 2008R2
有网友希望有人帮他优化一下他的SQL,SQL语句如下:
WITH T AS ( SELECT B.O_Money MON,B.O_States STATES FROM M_Basket A
JOIN M_OrderInfo B ON A.OrderID=B.ID WHERE A.GoodID=@GOODSID ), B AS ( SELECT (SELECT SUM(MON) FROM T)SumMoney, (SELECT SUM(MON) FROM T WHERE STATES IN (2,3,4))ComfirmMoney, (SELECT COUNT(*) FROM T WHERE STATES=2)AleadyDrive, (SELECT COUNT(*) FROM T WHERE STATES=3)AleadyPay, (SELECT COUNT(*) FROM T WHERE STATES=4)AleadyComfirm ) INSERT @BIAO SELECT * FROM B
看了一下语句,有可能出问题的地方,是with B 里面的内容,T表被访问了4次,
稍微转换一下思路,用case when来改写这段,就可以让T表只访问1次。
改写的SQL如下:
WITH T AS ( SELECT B.O_Money MON , B.O_States STATES FROM M_Basket A JOIN M_OrderInfo B ON A.OrderID = B.ID WHERE A.GoodID = @GOODSID ), B AS ( SELECT SUM(MON) AS SumMoney , SUM(CASE WHEN STATES IN ( 2, 3, 4 ) THEN MON END) AS ComfirmMoney , COUNT(CASE WHEN STATES = 2 THEN 1 END) AS AleadyDrive , COUNT(CASE WHEN STATES = 3 THEN 1 END) AS AleadyPay , COUNT(CASE WHEN STATES = 4 THEN 1 END) AS AleadyComfirm FROM T ) INSERT @BIAO SELECT * FROM B
(本文完)
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原文地址:http://www.cnblogs.com/boss-he/p/4647956.html