Question

更新数据库的一条sql语句怎么写

一个表为a 字段有 aid,quantity b表有字段 bid,aid
我现在要修改a表的quantity，quantity = b表中aid的个数，这条语句怎么写

Answer 1

update a set quantity = (select count(*) from b where a.aid = b.aid) where a.aid = b.aid

追问

Unknown column 'b.aid' in 'where clause'

追答

update a set quantity = c.counts from (select b.aid,count(*) as counts from b group by b.aid) c,a
where a.aid=c.aid
试试 不行再议