Question

我在语法上有困难...

这是我的查询：

SELECT t.diapason,
       Count(*) AS 'number_of_users'
FROM   (SELECT CASE
                 WHEN amount < 200 THEN '0-200'
                 WHEN amount >= 200 THEN '200 +'
               end AS diapason
        FROM   (SELECT Sum(amount) AS amount
                FROM   payments) p) t
GROUP  BY t.diapason
ORDER  BY number_of_users DESC;

但是现在我只需要选择在'2018-01-01'和'2018-01-12'之间具有activity.login_time的用户。

所以，我想我应该使用INNER JOIN并设置一段时间。怎么办？

我的桌子：

activity
user_id    login_time
1          01.01.2018
2          01.01.2018
3          03.01.2018
4          30.02.2018

payments
user_id    amount   payment_time
1          50       10.12.2017
1          200      09.12.2017
2          40        08.08.2017

我应该在查询中进行哪些更改以添加activity.login_time？

期间01.01.2018-12.01.2018的输出

diapason     number_of_users
0-200          2
200+           1

Answer 1

我理解您的问题。在01.01.2018-12.01.2018期间，您有3个用户（user_id = 1,2,3）登录。在这些用户中，user_id 1进行了2次付款，总计250次，user_id 2进行了1次付款，共40次付款，user_id 3进行了0次付款，因此其总值为0。因此，在0-200范围内有2个值，在{范围200 +。如果是正确的理解，此查询将为您提供所需的结果：

SELECT CASE  
         WHEN amount < 200 THEN '0-200'
         WHEN amount >= 200 THEN '200 +'
       END AS diapason,
       COUNT(*) AS number_of_users
FROM (SELECT a.user_id, COALESCE(SUM(p.amount), 0) AS amount
      FROM activity a
      LEFT JOIN payments p ON p.user_id = a.user_id
      WHERE a.login_time BETWEEN '01.01.2018' AND '12.01.2018'
      GROUP BY a.user_id) p
GROUP BY diapason;

输出：

diapason    number_of_users
0-200       2
200 +       1

SQLFiddle demo

更新

要添加总数为number_of_users的另一行，只需在WITH ROLLUP子句中添加GROUP BY：

SELECT CASE  
         WHEN amount < 200 THEN '0-200'
         WHEN amount >= 200 THEN '200 +'
       END AS diapason,
       COUNT(*) AS number_of_users
FROM (SELECT a.user_id, COALESCE(SUM(p.amount), 0) AS amount
      FROM activity a
      LEFT JOIN payments p ON p.user_id = a.user_id
      WHERE a.login_time BETWEEN '01.01.2018' AND '12.01.2018'
      GROUP BY a.user_id) p
GROUP BY diapason WITH ROLLUP

输出：

diapason    number_of_users
0-200       2
200 +       1
(null)      3

在您的应用程序框架中，您可以使用diapason值为NULL这样的事实来代替输出类似Total的内容。

Updated SQLFiddle

您也可以在MySQL中执行相同的操作（请参见此SQLFiddle），方法是将该查询包装为子查询，并在COALESCE列上使用diapason。在这种情况下，输出为：

diapason    number_of_users
0-200       2
200 +       1
Total       3

Answer 2

您添加WHERE子句进行过滤。

SELECT t.diapason,
       COUNT(*) AS 'number_of_users'
FROM (
    SELECT 
        CASE
            WHEN amount < 200 THEN '0-200'
            WHEN amount >= 200 THEN '200 +'
        END AS diapason
    FROM   (
        SELECT payments.user_id, SUM(amount) AS amount
        FROM   payments
        INNER JOIN activity ON payments.user_id = activity.user_idAND activity.login_time = payments.payment_time
        WHERE activity.login_time BETWEEN '2018-01-10' AND '2018-01-12'
        GROUP  BY payments.user_id
    ) p
) t
GROUP  BY t.diapason
ORDER  BY number_of_users DESC;

如何在查询中添加一些restrictios？

2 个答案: