SQL 的各种 join 用法

作者：C.L. Moffatt

http://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins

 

 

 

7种 join 用法

                         

 

 

                       

 

 

1.INNER JOIN（内连接）

                                        

 

SELECT <select_list>

FROM Table_A A

INNER JOIN Table_B B

ON A.Key = B.Key

 

 

 

2.LEFT JOIN（左连接）

                                        

 

SELECT <select_list>

FROM Table_A A

LEFT JOIN Table_B B

ON A.Key = B.Key

 

 

 

3.RIGHT JOIN（右连接）

                                        

 

SELECT <select_list>

FROM Table_A A

RIGHT JOIN Table_B B

ON A.Key = B.Key

 

 

 

4.OUTER JOIN（外连接）

                                        

SELECT <select_list>

FROM Table_A A

FULL OUTER JOIN Table_B B

ON A.Key = B.Key

 

 

 

5.LEFT JOIN EXCLUDING INNER JOIN   （左连接-排除内连接）

                                        

 

 

SELECT <select_list>

FROM Table_A A

LEFT JOIN Table_B B

ON A.Key = B.Key

WHERE B.Key IS NULL

 

 

 

6.RIGHT JOIN EXCLUDING INNER JOIN   （右连接-排除内连接）

                                            

 

 

SELECT <select_list>

FROM Table_A A

RIGHT JOIN Table_B B

ON A.Key = B.Key

WHERE A.Key IS NULL

 

 

7.OUTER JOIN EXCLUDING INNER JOIN （外连接-排除内连接）

                                            

 

SELECT <select_list>

FROM Table_A A

FULL OUTER JOIN Table_B B

ON A.Key = B.Key

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