php - 连接三个不同的表

Question

我正在尝试获取两个表的计数值并使用成员 ID 作为键来计算其他表的行数，到目前为止我有这段代码，但它为 comCount 输出一个大值，为 chatCount 输出空值。这是我的代码

SELECT members.*
, comments.commenter_id
, cb.user_id
, COUNT(comments.comment) AS comCount
, COUNT(cb.message) AS chatCount
FROM members 
INNER JOIN comments ON members.id = comments.commenter_id
INNER JOIN chat_box AS cb ON members.id = cb.user_id
WHERE members.id ='$profileId'`

Answer 1

SELECT  members.* , 
        a.commenter_id , 
        b.user_id , 
        a.totalComment , 
        b.totalChat
FROM    members 
        INNER JOIN 
        (
            SELECT commenter_id, COUNT(*) totalComment
            FROM comments
            GROUP BY commenter_id
        ) a ON members.id = a.commenter_id
        INNER JOIN 
        (
            SELECT user_id, COUNT(*) totalChat
            FROM chat_box 
            GROUP BY user_id            
        ) b  ON members.id = b.user_id
WHERE   members.id = '$profileId'

作为旁注，SQL Injection如果值（s）来自外部，则查询很容易受到攻击。请看下面的文章，了解如何预防。通过使用 PreparedStatements，您可以摆脱在值周围使用单引号。

• 如何防止PHP 中的 SQL 注入？

Answer 2

SELECT members.*
, comments.commenter_id
, cb.user_id
,(select  COUNT(1) from comments where commenter_id = members.id) AS comCount
,(select count(1) from chat_box where user_id = members.id) AS chatCount
FROM members 
WHERE members.id ='$profileId'`