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
关于join，你学废了么？
