postgresql - 如何获取 INNER join 的计数和所有项目的计数？

Question

我有两个表，paid_users 和 paid_users_no more。从本质上讲，付费用户可以拥有多个帐户。

他们的模式看起来像这样:

paid_users:
payor_id | user_email | payor_email | payment_start_date
---------------------------------------------------------
         |            |             |


paid_users_no_more:
user_id | payment_stop_date
---------------------------
        |

我写了一个查询来获取在给定月份(流失的账户)中哪些账户用于支付以及哪些账户不再支付:

SELECT payor_id, count(*) as "churned accounts" FROM paid_users_no_more 
INNER JOIN paid_users 
ON paid_users_no_more.user_id=paid_users.user_id 
WHERE paid_users.payment_start_date NOT BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
AND paid_users_no_more.payment_stop_date BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
GROUP BY paid_users.payor_id;

这为我提供了 8 月份每个 payor_id 的流失账户数量 - 我如何获取付款人拥有的账户总数？即，以下查询为我提供了每个 payor_id 的帐户数量:

SELECT paid_users.payor_email,count(*) AS "total accounts" 
FROM paid_users 
WHERE paid_users.payment_start_date NOT BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
GROUP BY paid_users.payor_email;

我希望能够以某种方式连接两个结果表以查看“流失账户”和“总账户”(因为我想计算流失收入，并且不知何故拥有的账户越多，它们的成本越低)- 有吗加入这些表的方法？

谢谢!

Answer 1

如果您使两个查询成为 Union Compatible，那么您可以将结果合并并与其他查询聚合:

    SELECT payer, 
           sum(churned_accounts) AS "churned_count",
           sum(total_accounts) AS "total_count" 
    FROM (
      SELECT CAST(payor_id AS CHAR(50)) AS "payer", 
             count(*) as "churned accounts", 
             0 AS "total accounts" 
      FROM paid_users_no_more 
      INNER JOIN paid_users 
        ON paid_users_no_more.user_id=paid_users.user_id 
      WHERE paid_users.payment_start_date NOT BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
      AND paid_users_no_more.payment_stop_date BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
      GROUP BY paid_users.payor_id

      UNION

      SELECT CAST(paid_users.payor_email AS CHAR(50)) AS "payer", 
             0 AS "churned accounts", 
             count(*) AS "total accounts" 
      FROM paid_users 
      WHERE paid_users.payment_start_date NOT BETWEEN '2015-08-01 00:00:00'::timestamp AND '2015-08-30 23:59:59'::timestamp 
      GROUP BY paid_users.payor_email
    ) as All_Accounts

0 AS "total_accounts" 和 0 AS "churned_accounts" 意味着两个查询具有相同的字段，这使得 UNION 可能。