mysql如何根据各自条件批量更新

问题描述

现有两张表，A是明细表id uid cost

0

1

4

3

现在要把把该表中cost大于0的数据，根据uid分组然后更新到另一个表上

select uid,count(cost) as count from A group by uid where cost > 0

这是取出的语句，有没办法一句话把这个查询结果根据uid更新到另一张表上？

问题解答

update B b set b.col=(select count(a.cost) as count from A a where cost > 0 and a.uid=b.uid group by uid)