数据库常用Join查询

1.查询A，B表共有部分内容：

SELECT <select_list>

FROM TableA A INNER JOIN TableB B ON A.Key = B.Key

2.查询A表所有和AB表共有部分：

SELECT <select_list>

FROM TableA A

LEFT JOIN Table B B

ON A.Key = B.Key

3.查询B表所有和AB表共有部分：

SELECT <select_list>

FROM TableA A

RIGHT JOIN TableB B

ON A.Key = B.Key

4.查询A表独有部分内容：

SELECT <select_list>

FROM TableA A

LEFT JOIN TableB B

ON A.Key = TableB B

ON A.Key = B.Key

WHERE B.Key IS NULL

5.查询B表独有部分:

SELECT <select_list>

FROM TableA A
RIGHT JOIN TableB B

ON A.Key = B.Key
WHERE A.Key IS NULL

6.查询AB表所有部分：

SELECT <sclect_list>

FROM TableA A
FULL OUTER JOIN TableB B

ON A.Key = B.Key

但MySQL不支持改语法操作，在MySQL中可使用

SELECT <select_list>

FROM TableA A

RIGHT JOIN TableB B

ON A.Key = B.Key

union

SELECT <select_list>

FROM TableA A

LEFT JOIN Table B B

ON A.Key = B.Key

完成查询

7.查询AB表各自独有部分：

SELECT<select_list>

FROM TableA A
FULL OUTER JOIN TableB B

ON A.Key = B.Key
WHERE A.Key IS NULL OR B.Key IS NULL