sql_表连接

1. 使用join连接多个查询：

     select * from A1 inner join A2 on A1.id = A2.id inner join A3 on A2.id = A3.id

2.修改A表中与B表中有相关关系的多条记录列

     update A set  A.name = 'simier' From (select * from B) as t where A.id = t.id