查询和三层有什么关系?你想怎么关联?--多表连接查询 select * from customer left join users on customer.Id=users.uId --左外连select * from customer inner join users on customer.Id=users.uId --内连接select * from customer FULL OUTER JOIN users on customer.Id=users.uId --内连接
2楼解释的相当清楚了、不过纠正下、 select * from customer FULL OUTER JOIN users on customer.Id=users.uId (这个是外连接、、)
查询和三层有什么关系?你想怎么关联?--多表连接查询
select * from customer left join users on customer.Id=users.uId --左外连select * from customer inner join users on customer.Id=users.uId --内连接select * from customer FULL OUTER JOIN users on customer.Id=users.uId --内连接
select * from customer FULL OUTER JOIN users on customer.Id=users.uId (这个是外连接、、)