连接三个表并检查记录

Question

如果用户有记录，我想连接三个表并检查另外两个表。

表格：

table1
id | username | is_active

table2
id | userid | amount

table3
id | userid | amount

我想获取并统计 'is_active' = 1 且表 2 和表 3 上没有记录的用户

我正在尝试这个：

SELECT c.id,c.is_active, 
       COUNT(c.id) AS count,
       COUNT(a.userid) AS count1,
       COUNT(b.userid) AS count2
FROM   `tbl_members` c 
       LEFT JOIN `table1` b 
              ON c.`id` = b.`userid` 
       LEFT JOIN `table2` a 
              ON b.`userid` = a.`userid` 
WHERE  c.`is_active` = 1 
GROUP BY c.id

Answer 1

这个怎么样？

select count(*) as count from
(SELECT distinct c.id
FROM   `tbl_members` c 
       LEFT JOIN `table1` b 
              ON c.`id` = b.`userid` 
       LEFT JOIN `table2` a 
              ON c.id = a.`userid` 
WHERE  c.`is_active` = 1 and a.userid is null and b.userid is null) s1

这会计算具有 is_active 集且没有对应的 a.userid 或 b.userid 的唯一 c.id。

实际上，您可以省略“distinct”，假设 c.id 是 tbl_members 的主键（因此是唯一键）。这样会更简单：

select count(*) 
FROM   `tbl_members` c 
       LEFT JOIN `table1` b 
              ON c.`id` = b.`userid` 
       LEFT JOIN `table2` a 
              ON c.id = a.`userid` 
WHERE  c.`is_active` = 1 and a.userid is null and b.userid is null