一个有意思的语句问题表A (id,m)表B (id,n)表c (id,n)select a.id ,a.m,(这里怎么写(要临时数据)条件是如果从跟表b,c中找到跟表a的id对应的n) n from a[解决办法]最好加点数据 看下效果 是这样?
select a.id, a.m, (select distinct n from (select b.n from b union all select c.n from c) where a.id=n) nfrom a