Question

当我尝试连接具有内部连接的表时..返回数据..但是当我连接4个表与完全外连接时，我说

错误：仅在合并可加入的连接条件“
支持FULL JOIN

示例查询：

SELECT hr_employee.name,hr_movement.amount,hr_concept.name,hr_period.name
FROM hr_employee
FULL OUTER JOIN hr_movement
ON hr_employee.ad_client_id=hr_movement.ad_client_id
FULL OUTER JOIN hr_concept
ON hr_movement.ad_client_id=hr_employee.ad_client_id
FULL OUTER JOIN hr_period
ON hr_concept.ad_client_id=hr_employee.ad_client_id

Answer 1

SELECT hr_employee.name,hr_movement.amount,hr_concept.name,hr_period.name
FROM hr_employee
FULL OUTER JOIN hr_movement
ON hr_employee.ad_client_id=hr_movement.ad_client_id
FULL OUTER JOIN hr_concept
ON hr_movement.ad_client_id=hr_employee.ad_client_id /*<- here*/
FULL OUTER JOIN hr_period
ON hr_concept.ad_client_id=hr_employee.ad_client_id /*<- and here*/

您正在加入表，但不要在连接条件中使用这些表。除此之外，MySQL不支持FULL OUTER JOINs。他们像在this answer中一样实现。

Answer 2

MySQL中没有FULL OUTER JOIN 。请参阅7.2.12. Outer Join Simplification和12.2.8.1. JOIN Syntax：

您可以使用模仿FULL OUTER JOIN UNION（来自MySQL 4.0.0）：

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

有三个表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

Source

查看here

错误：仅在合并可连接的连接条件下支持FULL JOIN

2 个答案: