mysql - 如何使用 mysql inner join 计算其他表中的行数？

Question

我有以下 3 个表:

crm_customers:

crm_progress:

crm_notifications:

我想要以下结果:

为了实现上述要求的输出，我使用了以下查询:

SELECT `cc`.`customer_id`, `cc`.`customer_name`, COUNT(`cp`.`progress_customer`) AS Progress, COUNT(`cn`.`notification_customer`) AS Notifications 
FROM `crm_customers` AS `cc` INNER JOIN `crm_progress` AS `cp` 
ON `cc`.`customer_id` = `cp`.`progress_customer` 
INNER JOIN `crm_notifications` AS `cn` 
ON `cn`.`notification_customer` = `cp`.`progress_customer` 
WHERE `cc`.`customer_id` = 1 AND `cc`.`customer_status` = 1 

但结果完全错了。但是，当我只加入 2 个表时，结果是准确的。

以下查询带来正确的输出:

SELECT `cc`.`customer_id`, `cc`.`customer_name`, COUNT(`cp`.`progress_customer`) AS Progress 
FROM `crm_customers` AS `cc` INNER JOIN `crm_progress` AS `cp` 
ON `cc`.`customer_id` = `cp`.`progress_customer` 
WHERE `cc`.`customer_id` = 1 AND `cc`.`customer_status` = 1

我哪里做错了？如何正确使用join获取需要的结果？

Answer 1

尝试下面的查询:你需要计算与特定客户相关联的 progress_id 和 notification_id

SELECT `cc`.`customer_id`, `cc`.`customer_name`, COUNT(distinct `cp`.`progress_id`) AS Progress, COUNT(distinct `cn`.`notification_id`) AS Notifications 
FROM `crm_customers` AS `cc` INNER JOIN `crm_progress` AS `cp` 
ON `cc`.`customer_id` = `cp`.`progress_customer` 
INNER JOIN `crm_notifications` AS `cn` 
ON `cn`.`notification_customer` = `cp`.`progress_customer` 
WHERE `cc`.`customer_id` = 1 AND `cc`.`customer_status` = 1 
group by `cc`.`customer_id`, `cc`.`customer_name`