Question

A,B,C 三张表 关系表B一对多 怎么取一对一 oracle

A表字段：userid,username;B表字段：userid,addid;C表字段：addid,address;B表中的同个userid可能对应多个addid;现要得到userid,username,address不能重复userid；addresss任意一个

Answer 1

select a.userid,a.username,max(c.address)
from A a,B b,C c where a.userid=b.userid and b.addid=c.addid
group by a.userid,a.username