Question

我有一个按字段描述分组的查询。（总共有9个描述。）我需要以某种方式将这些描述中的3个组合成一个组，总共给出了7个描述。我是sql查询的新手，所以到目前为止，我对JOINS和WHERE条款之外的任何事情都很失落。我很感激帮助。

SELECT        serviceclass.description, DATEPART(Year, meterread.readdate) AS Year, DATEPART(Month, meterread.readdate) AS Month, SUM(meterread.consumption) 
                     AS Consumption, COUNT(DISTINCT accountservice.account_id) AS Locations
FROM            accountservice INNER JOIN
                     serviceclass ON accountservice.serviceclass_id = serviceclass.serviceclass_id INNER JOIN
                     meterread ON accountservice.accountservice_id = meterread.accountservice_id
WHERE        (@Year = DATEPART(Year, meterread.readdate))
GROUP BY serviceclass.description, DATEPART(Year, meterread.readdate), DATEPART(Month,meterread.readdate)
ORDER BY Year, Month

Answer 1

您通常会使用case语句执行此操作，该语句同时包含select和group by语句。类似的东西：

select (case when serviceclass.description = 'A' then 'B'
             else serviceclass.description
        end) as description
       . . . -- fill in with query here
group by (case when serviceclass.description = 'A' then 'B'
             else serviceclass.description
           end), . . .  -- rest of query goes here

Answer 2

您可以使用CASE语句来实现此目的。

使用

替换serviceclass.desription和SELECT子句中的GROUP BY

CASE
    WHEN serviceclass.description IN ('Desc1','Desc2','Desc3')
        THEN 'JointDescription'
    ELSE serviceclass.description
END

并使用您的三个描述更新Desc 1~3，并将联合描述更新为您想要的内容。

结果：

SELECT CASE
           WHEN serviceclass.description IN ('Desc1','Desc2','Desc3')
               THEN 'JointDescription'
           ELSE serviceclass.description
       END as description, 
       DATEPART(Year, meterread.readdate) AS Year,  
       DATEPART(Month, meterread.readdate) AS Month, 
       SUM(meterread.consumption) AS Consumption, 
       COUNT(DISTINCT accountservice.account_id) AS Locations
FROM accountservice 
INNER JOIN serviceclass ON accountservice.serviceclass_id = serviceclass.serviceclass_id 
INNER JOIN meterread ON accountservice.accountservice_id = meterread.accountservice_id
WHERE        (@Year = DATEPART(Year, meterread.readdate))
GROUP BY CASE
             WHEN serviceclass.description IN ('Desc1','Desc2','Desc3')
                  THEN 'JointDescription'
             ELSE serviceclass.description
         END, 
         DATEPART(Year, meterread.readdate), 
         DATEPART(Month,meterread.readdate)
ORDER BY Year, Month

组合GROUP BY中的组

2 个答案: