1 /* 左连接 left join 或者 left outer join */
2 /* 左连接 Table_A表数据全部显示，Table_B根据条件匹配Table_A 匹配上显示，否则显示NULL */
3 SELECT * from Table_A
4 SELECT * from Table_B
5 SELECT * from Table_A a left outer join Table_B b on a.Code = b.Code
6
7
8
9 /* 右连接 right join 或者 right outer join */
10 /* 右连接 Table_B表数据全部显示，Table_A根据条件匹配Table_B 匹配上显示，否则显示NULL */
11 SELECT * from Table_A
12 SELECT * from Table_B
13 SELECT * from Table_A a right join Table_B b on a.Code = b.Code
14
15
16 /*完整外部联接:full join或full outer join*/
17 /*完整外部联接返回Table_A和Table_b中的所有行。当Table_A在Table_B表中没有匹配行时，
18 则Table_B的选择列表列包含空值。如果表之间有匹配行，则整个结果集行包含基表的数据值。*/
19 SELECT * from Table_A
20 SELECT * from Table_B
21 SELECT * from Table_A a full join Table_B b on a.Code = b.Code
22
23 /*内连接:join或 inner join*/
24 /*返回Table_A和Table_B中匹配的列*/
25 SELECT * from Table_A
26 SELECT * from Table_B
27 SELECT * from Table_A a join Table_B b on a.Code = b.Code
28
29 /* 交差连接 cross join */
30 /*交差连接返回的结果是 Table_A 和Table_B表的笛卡尔积(Table_A的行数乘以Table_B的行数) */
31 SELECT * from Table_A
32 SELECT * from Table_B
33 SELECT Count(*) from Table_A a cross join Table_B
34 SELECT * from Table_A a cross join Table_B
