Question

让我们说，我有3张桌子，汽车，车主和车主。现在我想要有完整的汽车清单，那些拥有车主和那些没有车的车。

当汽车拥有自己的车时，我必须拥有车主的数据。

Wrong query 1 (selects ownerless cars out): 
SELECT * FROM car 
LEFT JOIN cars_owner ON ...
INNER JOIN owner ON ...

Wrong query 2 (selects cars_owner relations without owners too): 
SELECT * FROM car 
LEFT JOIN cars_owner ON ...
LEFT JOIN owner ON ...

问题是：如何在mysql中加入一个带内连接的表？有什么想法吗？

Answer 1

此查询返回拥有所有者的汽车：

SELECT * FROM car
LEFT JOIN cars_owner ON (car.CarID=cars_owner.CarID)
inner join owner ON (owner.OwnID = cars_owner.OwnID)

然而，这将使车辆没有车主：

SELECT * FROM car
where (car.CarID!=(SELECT car.CarID FROM car
                   LEFT JOIN cars_owner ON (car.CarID=cars_owner.CarID)
                   inner join owner ON (owner.OwnID = cars_owner.OwnID)) )

表的组合左连接到mysql中的内连接

1 个答案: