Combination of table left join to an inner join in mysql

Question

Lets say, I have 3 tables, cars, cars_owner and owner. Now I want to have the complete list of cars, those that do have owners and those that don't.

When a car has an own, I must have the data of the owner.

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 ...

The question ist: How to left join a table with an inner join in mysql? Any ideas?

Answer 1

This Query returns the cars that have owners:

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

However this returns the cars without owners:

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)) )

Answer 2

You just need to nest the JOINs correctly:

SELECT * FROM car 
LEFT JOIN (cars_owner INNER JOIN owner ON cars_owner.owner_id = owner.owner_id
          ) ON car.car_id = cars_owner.car_id

The point is that you want all cars (so a left join on cars_owner), but only cars_owner that have an existing owner (so an inner join on owner).

The brackets make sure that the inner join is executed first. That is: Give me all cars, and from those car_owners that have an actual owner, show the owners (otherwise show them as NULL, but don't discard the whole car row).