本文作者：C.L. Moffatt

下圖展示了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相關的 7 種用法。

具體分解如下：

1.INNER JOIN（內連接）

SELECT <select_list> FROM Table_A A INNER JOIN Table_B B ON A.Key = B.Key

2.LEFT JOIN（左連接）

SELECT <select_list> FROM Table_A A LEFT JOIN Table_B B ON A.Key = B.Key

3.RIGHT JOIN（右連接）

SELECT <select_list> FROM Table_A A RIGHT JOIN Table_B B ON A.Key = B.Key

4.OUTER JOIN（外連接）

SELECT <select_list> FROM Table_A A FULL OUTER JOIN Table_B B ON A.Key = B.Key

5.LEFT JOIN EXCLUDING INNER JOIN（左連接-內連接）

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（右連接-內連接）

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（外連接-內連接）

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

總結

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