sql怎样连接join（一张图看懂SQL的各种）

作者：C.L. Moffatthttp://www.codeproject.com/Articles/33052/Visual-Representation-of-SQL-Joins

下图展示了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相关的 7 种用法。

具体分解如下：

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-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-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-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

,