[英]Select unique ids from multi values on one column in another table
我在一個問題上停留了幾個小時,這個問題可能很容易解決,但我迷失了……
我有3張桌子:
用戶
id name
----------
1 jack
2 john
...
汽車
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
例如,我想讓所有用戶在user_car表中擁有ID為1和2的汽車,因此我應該只獲得id_user 2,而我找不到正確的方法。
試試這個未經測試的查詢:
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
我將在此問題上使用UNION:
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)
也許你想要這個
SELECT *
FROM USER
WHERE id IN
(SELECT id_user
FROM user_car
WHERE id_car=1 OR id_car=2);
您可以使用COUNT來做到這一點:
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
請注意,當您僅使用汽車ID時,可以簡化此操作以消除對汽車桌子的需要。
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