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

Inner JOIN

SELECT

FROM Table_A A

INNER JOIN Table_B B

ON A.Key = B.Key

Left JOIN

SELECT

FROM Table_A A

LEFT JOIN Table_B B

ON A.Key = B.Key

Right JOIN

SELECT

FROM Table_A A

RIGHT JOIN Table_B B

ON A.Key = B.Key

Outer JOIN

SELECT

FROM Table_A A

FULL OUTER JOIN Table_B B

ON A.Key = B.Key

Left Excluding JOIN

SELECT

FROM Table_A A

LEFT JOIN Table_B B

ON A.Key = B.Key

WHERE B.Key IS NULL

Right Excluding JOIN

SELECT

FROM Table_A A

RIGHT JOIN Table_B B

ON A.Key = B.Key

WHERE A.Key IS NULL

Outer Excluding JOIN

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

更多内容可以参考 SQL 教程