从另一张表的一列中的多个值中选择唯一的ID

Question

I'm stuck for hours on an issue that might be pretty simple to solve but I'm just so lost...

I got 3 tables :

user

id    name
----------
1     jack
2     john
...

car

id    name
----------
1     ford
2     fiat
3     alfa
4     lada
...

user_car

id_user    id_car
-----------------
1          2
1          4
2          1
2          2
2          3

For example, i want to get all users with cars which have id 1 AND 2 in the user_car table so I should get the id_user 2 only and I can't find the proper way to do it.

Answer 1

try this untested query:

select * from user join user_car car1 on id =car1.user_id
join user_car car2 on id =car2.user_id  where car1.id_car=1 and car2.id_car=2

Answer 2

I would use UNION for this matter:

SELECT id as id_user from user where id in(1, 2)
UNION
SELECT id as id_car from car where id in (1, 2)

Answer 3

May be you want this

SELECT *
FROM USER
WHERE id IN
    (SELECT id_user
     FROM user_car
     WHERE id_car=1 OR id_car=2);

Answer 4

You can use COUNT to do this:-

SELECT user.name
FROM user
INNER JOIN user_car ON user.id = user_car.id_user
INNER JOIN car ON user_car.id_car = car.id
WHERE car.id IN (1,2)
GROUP BY user.name
HAVING COUNT(DISTINCT car.id) = 2 

Note that this could be simplified to remove the need for the car table when you are just using the id of the car.