下图展现了 LEFT JOIN、RIGHT JOIN、INNER JOIN、OUTER JOIN 相干的 7 种用法。

具体合成如下：

1.INNER JOIN（内连贯）

SELECT <select_list> FROM Table_A AINNER JOIN Table_B BON A.Key = B.Key

2.LEFT JOIN（左连贯）

SELECT <select_list>FROM Table_A ALEFT JOIN Table_B BON A.Key = B.Key

3.RIGHT JOIN（右连贯）

SELECT <select_list>FROM Table_A ARIGHT JOIN Table_B BON A.Key = B.Key

4.OUTER JOIN（外连贯）

SELECT <select_list>FROM Table_A AFULL OUTER JOIN Table_B BON A.Key = B.Key

5.LEFT JOIN EXCLUDING INNER JOIN（左连贯-内连贯）

SELECT <select_list> FROM Table_A ALEFT JOIN Table_B BON A.Key = B.KeyWHERE B.Key IS NULL

6.RIGHT JOIN EXCLUDING INNER JOIN（右连贯-内连贯）

SELECT <select_list>FROM Table_A ARIGHT JOIN Table_B BON A.Key = B.KeyWHERE A.Key IS NULL

7.OUTER JOIN EXCLUDING INNER JOIN（外连贯-内连贯）

SELECT <select_list>FROM Table_A AFULL OUTER JOIN Table_B BON A.Key = B.KeyWHERE A.Key IS NULL OR B.Key IS NULL

对于join，你学废了么？