SQL查询——7种JOIN方法1张图

SQL 是用于访问和处理数据库的标准的计算机语言。表关联查询会经常用到，以下是 7 种关联查询区分：

Inner JOIN

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

Left JOIN

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

Right JOIN

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

Outer JOIN

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

Left Excluding JOIN

SELECT
	< select_list >
FROM
	Table_A A
	LEFT JOIN Table_B B ON A.KEY = B.KEY
WHERE
	B.KEY IS NULL

Right Excluding JOIN

SELECT
	< select_list >
FROM
	Table_A A
	RIGHT JOIN Table_B B ON A.KEY = B.KEY
WHERE
	A.KEY IS NULL

Outer Excluding JOIN

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