SQL 服务器查询语法，用于计算变量的最大出现次数并输出相同的

Question

我正在使用 SQL Server 2014，我有一个简单的查询，如果我运行它与相关 table 相对应，它会给我以下输出。所以这是查询：

use MyDatabase

select ReservationStayID
       , NonRoomBundleID
       ,StayDate

from ResStayNonRoomBundle

where ReservationStayID = 11676

输出如下：

ReservationStayID   NonRoomBundleID     StayDate
 11676                   2              2014-07-23 00:00:00.000
 11676                   2              2014-07-24 00:00:00.000
 11676                   2              2014-07-25 00:00:00.000
 11676                   2              2014-07-26 00:00:00.000
 11676                   2              2014-07-27 00:00:00.000
 11676                   2              2014-07-28 00:00:00.000
 11676                   4              2014-07-29 00:00:00.000
 11676                   4              2014-07-30 00:00:00.000
 11676                   4              2014-07-31 00:00:00.000
 11676                   4              2014-08-01 00:00:00.000
 11676                   4              2014-08-02 00:00:00.000
 11676                   4              2014-08-03 00:00:00.000
 11676                   4              2014-08-04 00:00:00.000
 11676                   1              2014-08-05 00:00:00.000

现在，我需要修改查询以获得以下输出：

ReservationStayID   NonRoomBundle ID    MTH

       11676            2               July 2014
       11676            4               August 2014

这就是我所做的：

USE MyDatabase
select ReservationStayID,max(NonRoomBundleID) AS [NonRoomBundle  ID],datename(m,StayDate) + ' ' + cast(datepart(yyyy,StayDate) as varchar) as  [MTH] 

from ResStayNonRoomBundle

where ReservationStayID = 11676

group by datename(m,StayDate) + ' ' + cast(datepart(yyyy,StayDate) as varchar), ReservationStayID

它给了我以下输出：

ReservationStayID   NonRoomBundle ID    MTH
       11676            4               July 2014
       11676            4               August 2014

我需要将 max(NonRoomBundleID) 更改为逻辑，输出出现次数最多的 'NonRoomBundleID' 而不仅仅是最大值。

换句话说，我希望查询计算每个月 NonRoomBundleID 的最大出现次数并输出那个。在 2014 年 7 月的情况下，出现次数最多的 NonRoomBundleID 是 2。因此，我希望查询输出 2 作为 2014 年 7 月的结果。

可能正在使用 COUNT 函数？如果是，我如何将它实现到我现有的查询中？

Answer 1

试试这个：

SELECT  ReservationStayID, NonRoombundleID, Tot, 
   CONVERT(VARCHAR, DATEPART(yyyy, DATEADD(month,  M,'1970-1-1')))+'-'+CONVERT(VARCHAR,DATEPART(month, DATEADD(month,  M,'1970-1-1'))) AS [Month] 
FROM 
   (
    SELECT ReservationStayID, NonRoombundleID, COUNT(*) AS Tot,   
     DATEDIFF(month, '1970-1-1', staydate) m, 
     ROW_NUMBER() OVER (
             partition by ReservationStayID, 
             DATEDIFF(month, '1970-1-1', staydate)  
             ORDER BY Count(*) DESC
             )  AS rownum
     FROM ResStayNonRoomBundle
     GROUP BY ReservationStayID, NonRoombundleID,
             DATEDIFF(month, '1970-1-1', staydate) 
    )  
    e 
 WHERE rownum =1

要使用您自己的月份格式：

SELECT  ReservationStayID, NonRoombundleID, Tot, 
   datename(m,DATEADD(MONTH, M, '1970-1-1')) + ' ' + cast(datepart(yyyy,DATEADD(MONTH, M,'1970-1-1')) as varchar)
FROM 
   (
    SELECT ReservationStayID, NonRoombundleID, COUNT(*) AS Tot,   
     DATEDIFF(month, '1970-1-1', staydate) m, 
     ROW_NUMBER() OVER (partition by ReservationStayID, DATEDIFF(month, '1970-1-1', staydate)  order by Count(*) DESC)  As rownum
     FROM ResStayNonRoomBundle
     GROUP BY ReservationStayID, NonRoombundleID, DATEDIFF(month, '1970-1-1', staydate) 
    ) 
    e 
 WHERE rownum =1

如果您想列出每个月的所有热门地点，试试这个：

SELECT  ReservationStayID, NonRoombundleID, Tot, 
   datename(m,DATEADD(MONTH, M, '1970-1-1')) + ' ' + cast(datepart(yyyy,DATEADD(MONTH, M,'1970-1-1')) as varchar) [Month]
FROM 
   (
    SELECT ReservationStayID, NonRoombundleID, COUNT(*) AS Tot,   
     DATEDIFF(month, '1970-1-1', staydate) m
     FROM ResStayNonRoomBundle L
     GROUP BY ReservationStayID, NonRoombundleID, DATEDIFF(month, '1970-1-1', staydate) 
     HAVING COUNT(*) = (
        SELECT MAX(Tot) FROM  (
           SELECT COUNT(*) AS Tot 
           FROM ResStayNonRoomBundle T
           WHERE DATEDIFF(month, '1970-1-1', T.staydate)  = DATEDIFF(month, '1970-1-1', L.staydate) 
           GROUP BY ReservationStayID, NonRoombundleID
           ) c
        )
     )
    e 
ORDER BY m

SQL 服务器查询语法，用于计算变量的最大出现次数并输出相同的

SQL Server Query syntax to count maximum occurrences of a variable and output same

sql-server

max