MySQL中没有FULL OUTER JOIN.参见 7.2.12.简化外部连接和 12.2.8.1. JOIN语法:

There is no FULL OUTER JOIN in MySQL. See 7.2.12. Outer Join Simplification and 12.2.8.1. JOIN Syntax:

您可以使用以下方式模拟FULL OUTER JOIN UNION(从MySQL 4.0.0开始):

You can emulate FULL OUTER JOIN using UNION (from MySQL 4.0.0 on):

有两个表t1，t2:

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id

具有三个表t1，t2，t3:

with three tables t1, t2, t3:

SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
LEFT JOIN t3 ON t2.id = t3.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
LEFT JOIN t3 ON t2.id = t3.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
RIGHT JOIN t3 ON t2.id = t3.id