结果是这样,楼主自己看需要那个吧: select * from a aid adata 1 1 2 2 3 3 4 4select * from b bid bdata 3 3 4 4 5 5 6 6select * from a a full join b b on a.aid=b.bid //这是full join aid adata bid bdata 1 1 NULL NULL 2 2 NULL NULL 3 3 3 3 4 4 4 4 NULL NULL 5 5 NULL NULL 6 6select * from a a inner join b b on a.aid=b.bid//这是inner join aid adata bid bdata 3 3 3 3 4 4 4 4
LEFT JOIN C_User_Premission B ON A.role_pid=B.pre_id
select a.*,b.* from C_User_Role_Premission a inner join C_User_Premission b on
a.role_pid=b.pre_id
select * from C_User_Role_Premission ,C_User_Premission where C_User_Role_Premission.role_pid=C_User_Premission.pre_id
select a.*,b.* from C_User_Role_Premission as a inner join C_User_Premission as b on
a.role_pid=b.pre_id
但是我看楼主要的是两个表的全部信息。所以用了个full join, 这个取出来的是两个表所有的信息,当条件(C_User_Role_Premission.role_pid=C_User_Premission.pre_id)满足时,是一条记录,当不满足时(也就是两个表中不满足的字段)则为null
select * from a
aid adata
1 1
2 2
3 3
4 4select * from b
bid bdata
3 3
4 4
5 5
6 6select * from a a full join b b on a.aid=b.bid //这是full join
aid adata bid bdata
1 1 NULL NULL
2 2 NULL NULL
3 3 3 3
4 4 4 4
NULL NULL 5 5
NULL NULL 6 6select * from a a inner join b b on a.aid=b.bid//这是inner join
aid adata bid bdata
3 3 3 3
4 4 4 4