在MySql中有多个表的多个查询

Question

我有4个表，以及如何在查询结果时创建。

表格卡

id name
1 card1
2 card2
3 card3
4 card4

表格访问

id card_id
1     1
2     1
3     1
4     1
5     2
6     2
7     3
8     4

表格喜欢

id card_id
1     1
2     2
3     2
4     2
5     3
6     3
7     3
8     4

表最喜欢的

id card_id
1     1
2     1
3     1
4     1
5     3
6     3
7     3
8     4

结果

 name visit  like favorite
 card1   4      1      4
 card2   2      3      0
 card3   1      3      3
 card4   1      1      1

Answer 1

SELECT C.Name,
(SELECT COUNT(*) FROM VISIT AS V WHERE V.Card_Id = C.Id) AS Visits,
(SELECT COUNT(*) FROM `LIKE` AS L WHERE L.Card_Id = C.Id) AS Likes,
(SELECT COUNT(*) FROM FAVORITE AS F WHERE F.Card_Id = C.Id) AS Favorite
FROM Card AS C

Answer 2

我会使用此查询：

SELECT
  card.name,
  SUM(visit) AS visit,
  SUM(`like`) AS `like`,
  SUM(favorite) AS favorite
FROM
  card INNER JOIN
  (
    SELECT card_id, COUNT(*) as visit, 0 as `like`, 0 as favorite
    FROM visit
    GROUP BY card_id
    UNION ALL
    SELECT card_id, 0 as visit, COUNT(*) as `like`, 0 as favorite
    FROM `like`
    GROUP BY card_id
    UNION ALL
    SELECT card_id, 0 as visit, 0 as `like`, COUNT(*) as favorite
    FROM favorite
    GROUP BY card_id
  ) counts ON card.id = counts.card_id
GROUP BY card.id, card.name