数据准备：
create table T1( A varchar(10) not null, B varchar(10) not null, C tinyint not null ); create table T2( B varchar(10) not null, E tinyint not null ); insert into T1 values ('a1', 'b1', 5), ('a1', 'b2', 6), ('a2', 'b3', 8), ('a2', 'b4', 12); insert into T2 values ('b1', 3), ('b2', 7), ('b3', 10), ('b3', 2), ('b5', 2); select * from T1; select * from T2;
结果：
1 A B C 2 ---------- ---------- ---- 3 a1 b1 5 4 a1 b2 6 5 a2 b3 8 6 a2 b4 12 7 8 (4 行受影响) 9 10 B E 11 ---------- ---- 12 b1 3 13 b2 7 14 b3 10 15 b3 2 16 b5 2 17 18 (5 行受影响)
1、内连接
1 select * from T1 inner join T2 on T1.B = T2.B 2 3 A B C B E 4 ---------- ---------- ---- ---------- ---- 5 a1 b1 5 b1 3 6 a1 b2 6 b2 7 7 a2 b3 8 b3 10 8 a2 b3 8 b3 2
2、左外连接
1 select * from T1 left outer join T2 on T1.B = T2.B 2 3 A B C B E 4 ---------- ---------- ---- ---------- ---- 5 a1 b1 5 b1 3 6 a1 b2 6 b2 7 7 a2 b3 8 b3 10 8 a2 b3 8 b3 2 9 a2 b4 12 NULL NULL
3、右外连接
1 select * from T1 right outer join T2 on T1.B = T2.B 2 3 A B C B E 4 ---------- ---------- ---- ---------- ---- 5 a1 b1 5 b1 3 6 a1 b2 6 b2 7 7 a2 b3 8 b3 10 8 a2 b3 8 b3 2 9 NULL NULL NULL b5 2
4、完全连接
1 select * from T1 full outer join T2 on T1.B = T2.B 2 3 A B C B E 4 ---------- ---------- ---- ---------- ---- 5 a1 b1 5 b1 3 6 a1 b2 6 b2 7 7 a2 b3 8 b3 10 8 a2 b3 8 b3 2 9 a2 b4 12 NULL NULL 10 NULL NULL NULL b5 2
5、交叉连接（笛卡尔乘积）
1 select * from T1 cross join T2 2 3 A B C B E 4 ---------- ---------- ---- ---------- ---- 5 a1 b1 5 b1 3 6 a1 b1 5 b2 7 7 a1 b1 5 b3 10 8 a1 b1 5 b3 2 9 a1 b1 5 b5 2 10 a1 b2 6 b1 3 11 a1 b2 6 b2 7 12 a1 b2 6 b3 10 13 a1 b2 6 b3 2 14 a1 b2 6 b5 2 15 a2 b3 8 b1 3 16 a2 b3 8 b2 7 17 a2 b3 8 b3 10 18 a2 b3 8 b3 2 19 a2 b3 8 b5 2 20 a2 b4 12 b1 3 21 a2 b4 12 b2 7 22 a2 b4 12 b3 10 23 a2 b4 12 b3 2 24 a2 b4 12 b5 2