用一张图看懂 SQL 的各种 join 用法分享

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

FROM Table_A A

INNER JOIN Table_B B

ON A.Key = B.Key

2.LEFT JOIN（左连接）

SELECT

FROM Table_A A

LEFT JOIN Table_B B

ON A.Key = B.Key

3.RIGHT JOIN（右连接）

SELECT

FROM Table_A A

RIGHT JOIN Table_B B

ON A.Key = B.Key

4.OUTER JOIN（外连接）

SELECT

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

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

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

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