有这么一条sql

UPDATE product set BuyerCount =BuyerCount+1 where ProductId in( SELECT ProductId from orderproductdetail where OrderId=2014042514163700856 );

在数据为几欠条的情况下耗时为20多秒。把这条语句拆分之后

SELECT ProductId from orderproductdetail where OrderId=2014042514163700856

耗时0.01秒 结果为:2012

UPDATE product set BuyerCount =BuyerCount+1 where ProductId in(2012)

耗时0.02秒。这就奇怪了,两个时间都很短,为啥放一起就那么长时间。

下面总结了三种优化方法:

连表
UPDATE product p, orderproductdetail o set p.BuyerCount =p.BuyerCount+1 where p.ProductId=o.ProductId and o.OrderId=2014042514163700856;

连表的另一种形式
UPDATE product p INNER JOIN orderproductdetail o on p.ProductId=o.ProductId set p.BuyerCount =p.BuyerCount+1 where o.OrderId=2014042514163700856;

将子查询又起了一个别名查询了一遍
UPDATE product set BuyerCount =BuyerCount+1 where ProductId in( SELECT ProductId from (SELECT ProductId from orderproductdetail where OrderId=2014042514163700856) as tttt );

执行结果如下:

[SQL] UPDATE product p, orderproductdetail o set p.BuyerCount =p.BuyerCount+1 where p.ProductId=o.ProductId and o.OrderId=2014042514163700856;

受影响的行: 1

时间: 0.053ms

[SQL]

UPDATE product p INNER JOIN orderproductdetail o on p.ProductId=o.ProductId set p.BuyerCount =p.BuyerCount+1 where o.OrderId=2014042514163700856;

受影响的行: 1

时间: 0.053ms

[SQL]

UPDATE product set BuyerCount =BuyerCount+1 where ProductId in( SELECT ProductId from (SELECT ProductId from orderproductdetail where OrderId=2014042514163700856) as tttt );

受影响的行: 1

时间: 0.072ms
————————————————
版权声明:本文为CSDN博主「weixin_39611208」的原创文章,遵循CC 4.0 BY-SA版权协议,转载请附上原文出处链接及本声明。
原文链接:https://blog.csdn.net/weixin_39611208/article/details/113342068