Question

我有这3张桌子

users [ id , username, password ]
logs [ id, user_id, action ]
user_propeties [ id, user_id, prop_name, prop_value ]

我想用Count（logs.id）和count（user_propeties.id）选择所有用户的列只有在2个表中prop_value IS为空时，具体取决于用户ID

我有以下查询

SELECT t1.*, count(t2.`id`) as total_logs,count(t3.`id`) as total_propeties
                       FROM `users` t1
                       LEFT JOIN `user_propeties` t2
                                ON t1.`id` = t2.`user_id` AND ISNULL(t2.`prop_value`)
                       LEFT JOIN `logs` t3
                                ON t3.`user_id` = t1.`id`                                       
                       GROUP BY t1.id
                       ORDER BY t1.id DESC

返回行但计数值错误。我做错了什么？谢谢

Answer 1

我怀疑你想要一些DISTINCT，否则它将返回所有日志和属性组合的计数;

SELECT t1.*, COUNT(DISTINCT t2.`id`) as total_logs,
             COUNT(DISTINCT t3.`id`) as total_propeties
FROM `users` t1
LEFT JOIN `user_propeties` t2
         ON t1.`id` = t2.`user_id` AND ISNULL(t2.`prop_value`)
LEFT JOIN `logs` t3
         ON t3.`user_id` = t1.`id`                                       
GROUP BY t1.id
ORDER BY t1.id DESC

MySQL左连接多个计数

1 个答案: