MySQL 中没有 FULL OUTER JOIN.请参阅 7.2.12.外连接简化和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:

你可以模拟 FULL OUTER JOIN 使用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:

with two tables 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

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