Question

我有2个表：表1（用户）包含用户/领导者的姓名，表2（交易）包含用户交易记录，其列名为“原因”

有几个“原因”可以分为两类。

User Table
--------------
User   Leader
--------------
user1  Leader1
user2  Leader1
user3  Leader2
user4  Leader2


Transaction Table
-----------------------------------
User   Leader   Reason
-----------------------------------
user1  Leader1  Category 1 Reason 1
user1  Leader1  Category 1 Reason 1
user1  Leader1  Category 1 Reason 2
user1  Leader1  Category 1 Reason 2
user1  Leader1  Category 2 Reason 1
user1  Leader1  Category 2 Reason 1
user2  Leader1  Category 1 Reason 1
user2  Leader1  Category 1 Reason 1
user2  Leader1  Category 2 Reason 1
user2  Leader1  Category 2 Reason 1

我正在尝试计算用户进行的交易次数，并将其分为这两个类别。

我尝试了以下代码，该代码可以得到类别1原因的计数，但是仅显示具有该原因的用户。我的目的还在于向用户显示没有该原因但计数为0的用户。该查询也没有计算类别2原因（即使不打破这个简单的原因，我什至无法接近该值）

SELECT DISTINCT User.name, User.Leader, COUNT (reason) AS Reason FROM  
Transactions AS TRACKER 
INNER JOIN User AS GROUPS ON TRACKER.name=User.name
WHERE TRACKER.reason IN ('Category 1 Reason 1','Category 1 Reason 2','Category 1 Reason 3')
GROUP BY GROUPS.name, GROUPS.Leader

我的预期结果是：

--------------------------------------
User   Leader  Category 1   Category 2
--------------------------------------
User1  Leader1     4           2
User2  Leader1     2           2
User3  Leader2     0           0
User4  Leader2     0           0

但是我得到了：

-------------------------
User   Leader  Category 1   
-------------------------
User1  Leader1     4          
User2  Leader1     2

在此先感谢您的帮助

Answer 1

我认为您需要条件聚合：

SELECT u.name, u.Leader, 
       SUM(CASE WHEN t.reason IN ('Category 1 Reason 1', 'Category 1 Reason 2', 'Category 1 Reason 3') THEN 1 ELSE 0 END) AS reason_count
FROM User u LEFT JOIN
     Transactions t 
     ON t.name = u.name
GROUP BY u.name, u.Leader;

请注意，如果根本没有事务，这也将使用LEFT JOIN将所有行保留在users中。

如果出于每个类别的原因想要单独的列，请扩展上述逻辑：

SELECT u.name, u.Leader, 
       SUM(CASE WHEN t.reason IN ('Category 1 Reason 1') THEN 1 ELSE 0 END) as reason1_cnt,
       SUM(CASE WHEN t.reason IN ('Category 1 Reason 2') THEN 1 ELSE 0 END) as reason2_cnt,
       SUM(CASE WHEN t.reason IN ('Category 1 Reason 3') THEN 1 ELSE 0 END) as reason3_cnt
FROM User u LEFT JOIN
     Transactions t 
     ON t.name = u.name
GROUP BY u.name, u.Leader;

计算特定值的实例数，然后将结果与另一个表连接

1 个答案: