从动态表中选择时更改列名

Posted 2023-03-24

【中文标题】从动态表中选择时更改列名

【英文标题】：change the column name while selecting from dyanamic table

【发布时间】：2013-05-03 13:22:59

【问题描述】：

您好，我有考勤查询，它将使用 PIVOT 功能生成考勤报告

程序如下：

declare  @in_date DATETIME       

/*Select all the stagign entries related to promotion id and investment type id */    
  /* also only those staging daat related interface status tracking*/

  -- Getting all distinct dates into a temporary table #Dates
    SELECT a.date as full_date_of_attendence INTO #Dates
    FROM dbo.getFullmonth(@in_date) a
    ORDER BY a.date



    -- The number of days will be dynamic. So building
    -- a comma seperated value string from the dates in #Dates
    SELECT  @cols = COALESCE(@cols + ',[' + CONVERT(varchar, full_date_of_attendence, 106)
                                    + ']','[' + CONVERT(varchar, full_date_of_attendence, 106) + ']')
    FROM    #Dates
    ORDER BY full_date_of_attendence


    --select @cols

    ---- Building the query with dynamic dates

SET @qry =
    'SELECT * FROM
    (SELECT admission_id, attendence_status , date_of_attendence
    FROM dbo.tblattendence)emp
    PIVOT (MAX(attendence_status) FOR date_of_attendence IN (' + @cols + ')) AS stat'    



    -- Executing the query
    EXEC(@qry)

    -- Dropping temporary tables
    DROP TABLE #Dates

这是上面查询的输出::

admission_id    01 May 2013 02 May 2013 03 May 2013
2                NULL               1               0
3                NULL               1               1
4                NULL               0               0
5                NULL               0               1

这里我想把列的名字改成01,02,03...... 我希望值 1 作为 'P' 和 0 作为 'A'

谁能帮我实现这个目标？？

【问题讨论】：

使用 Select admission_id 作为 AdmsnId FROM dbo.tblattendence

【参考方案1】：

我建议对您的代码进行以下更改。如果您想要日期列表（1、2、3 等），则可以使用 DAY 函数。

通常，当我动态获取列列表时，我的首选是使用STUFF 和FOR XML PATH，我会将该代码更改为以下内容：

select @colsPiv = STUFF((SELECT ',' + QUOTENAME(cast(day(full_date_of_attendence) as varchar(2))) 
                from #Dates
                GROUP BY full_date_of_attendence
                ORDER BY full_date_of_attendence
        FOR XML PATH(''), TYPE
        ).value('.', 'NVARCHAR(MAX)') 
    ,1,1,'')

然后，如果您想用A 替换0 和用1 替换P，您将需要创建一个查询来获取用于替换值的列列表：

select @colsSel = STUFF((SELECT ', case when ' + QUOTENAME(cast(day(full_date_of_attendence) as varchar(2)))+'= 1 then ''P'' else ''A'' end as '+QUOTENAME(cast(day(full_date_of_attendence) as varchar(2)))
                      from #Dates
                      GROUP BY full_date_of_attendence
                      ORDER BY full_date_of_attendence
                FOR XML PATH(''), TYPE
                ).value('.', 'NVARCHAR(MAX)') 
                ,1,1,'')

基本上，这是创建一个类似于此的选择列表：

select case when [1] = 1 then 'P' else 'A' end as [1], ...

那么您的最终查询将是：

SET @qry =
'SELECT admission_id, '+@colsSel +' 
 FROM
 (
    SELECT admission_id, 
      attendence_status , 
      day(date_of_attendence) date_of_attendence
    FROM dbo.tblattendence
 )emp
 PIVOT 
 (
    MAX(attendence_status) 
    FOR date_of_attendence IN (' + @colsPiv + ')
 ) AS stat'   

见SQL Fiddle with Demo

【参考方案2】：

让我们只改变你想要的两件事，即

CONVERT(CHAR(2), full_date_of_attendence, 106) -- 使用 CHAR(2) 代替 varchar CASE attendence_status when 1 then 'P' else 'A' END 在 SELECT...

更改最少的代码。希望这可以帮助您了解将来如何对其他代码进行类似的更改。

declare @in_date DATETIME

/*Select all the stagign entries related to promotion id and investment type id */    
/* also only those staging daat related interface status tracking*/

-- Getting all distinct dates into a temporary table #Dates
SELECT a.date as full_date_of_attendence INTO #Dates
FROM dbo.getFullmonth(@in_date) a
ORDER BY a.date



-- The number of days will be dynamic. So building
-- a comma seperated value string from the dates in #Dates
SELECT  @cols = COALESCE(@cols + ',', '') + [' +
        CONVERT(CHAR(2), full_date_of_attendence, 106) + ']'
FROM    #Dates
ORDER BY full_date_of_attendence


--select @cols

---- Building the query with dynamic dates

SET @qry =
'SELECT * FROM
(SELECT admission_id, CASE attendence_status when 1 then 'P' else 'A' END, date_of_attendence
FROM dbo.tblattendence)emp
PIVOT (MAX(attendence_status) FOR date_of_attendence IN (' + @cols + ')) AS stat'    



-- Executing the query
EXEC(@qry)

-- Dropping temporary tables
DROP TABLE #Dates