如何内部连接三个表并进行计数


how to inner join three tables and get count

我有三个表:

members (id, name, surname, usr_img)
user_uploads (imgID, user_id, filename, description, up_time)
img_likes (likeID, img_id, user_id)

我需要从user_uploads中获取所有信息,并使用img_id从成员中获取上传者信息,并在img_likes表中进行2次计数(检查user_id(来自会话变量)和img_id是否存在,并获取img总点赞数)。

SELECT user_uploads.* AS uu, members.*, COUNT(img_id, user_id) AS usr_liked, COUNT(img_id) AS total_likes
FROM user_uploads
INNER JOIN members AS m ON m.id = uu.user_id -- owner info
INNER JOIN img_likes AS il ON il.img_id = uu.imgID AND il.user_id = ? -- check if logged in user already liked
INNER JOIN img_likes AS ilt ON ilt.img_id = uu.imgID -- total likes
GROUP BY img_id, user_id
ORDER BY up_time DESC

我不需要从img_id中获得任何信息,只需计算行数即可。我不知道是否需要内部联接,也许是为了指定user_id?

并获取计数:

$usr_liked = row['usr_liked'];
$total_likes = rwo['total_likes'];

这样行吗?

编辑:添加新查询:

SELECT
    user_uploads.*,
    (
        SELECT *
        FROM members m
        WHERE m.id = user_uploads.user_id
    ),
    (
        SELECT COUNT(*)
        FROM img_likes t
        WHERE t.img_id = user_uploads.imgID AND t.user_id = ?
    ) AS user_likes,
    (
        SELECT COUNT(*)
        FROM img_likes t
        WHERE t.img_id = user_uploads.imgID
    ) AS total_likes
FROM user_uploads
ORDER BY up_time DESC

您可以使用子查询:

SELECT 
    uu.*, 
    m.*,
    (
        SELECT COUNT(t.*)
        FROM img_likes t
        WHERE t.img_id = uu.imgID AND t.user_id = ?
    ) AS user_likes,
    (
        SELECT COUNT(t.*)
        FROM img_likes t
        WHERE t.img_id = uu.imgID 
    ) AS total_likes
FROM 
    user_uploads AS uu
    INNER JOIN members AS m ON 
        m.id = uu.user_id
ORDER BY
    uu.up_time DESC