列的類型「」與UNPIVOT列表中指定的其他列的類型衝突

Question

我已經編寫了此查詢以從整個表中動態查找數值的最大值或最小值。我的查詢是這樣的：

declare @col varchar(2000) 

set @col = STUFF((select ',' +' [' + c.name + ']' FROM 
    sys.columns c 
    INNER JOIN 
    sys.types t ON c.user_type_id = t.user_type_id 
WHERE 
    c.object_id = OBJECT_ID('JRR_20170301_Stg') 
    and c.system_type_id = 108 for XML path('')),1,1, '') 

    select @col -- This returns the column name and good. 

--However, the problem starts from here below 
    declare @sql varchar(max) 

set @sql='SELECT max(col) 
FROM JRR_20170301_Stg unPIVOT (col for ListofColumns in ('+@col+')) as unpivat' 

    exec (@sql) 

這裏是我的表結構：

CREATE TABLE [dbo].[JRR_20170301_Stg](
[col1] [numeric](7, 0) NULL, 
[col2] [numeric](7, 0) NULL, 
[col3] [varchar](30) NULL, 
[TIMESTAMP1] [varchar](8) NULL, 
[BRANCH] [varchar](2) NULL, 
[COE] [varchar](8) NULL, 
[SCHEME] [varchar](3) NULL, 
[NO] [varchar](7) NULL, 
[PLAN] [varchar](5) NULL, 
[ACODE] [varchar](8) NULL, 
[ACTNAME] [varchar](30) NULL, 
[SRNAME] [varchar](30) NULL, 
[OTHERNAME] [varchar](30) NULL, 
[ACTWTCH] [varchar](1) NULL, 
[EMPLC] [varchar](5) NULL, 
[EMPLNO] [varchar](13) NULL, 
[LADATE] [numeric](7, 0) NULL, 
[EARN] [numeric](7, 2) NULL, 
[REGPA] [numeric](7, 2) NULL, 
[OTAMT] [numeric](7, 2) NULL, 
[EMPSTAT] [varchar](1) NULL, 
[RESVE5] [varchar](100) NULL 
) ON [PRIMARY] 

有什麼辦法來糾正這個錯誤，並得到想要的結果？我可以使用交叉應用或其他？

Answer 1

使用unpivat所有字段應該是相同的類型。您需要使用CAST或CONVERT函數來製作它。

declare @col varchar(2000) 
declare @colCAST varchar(4000) 

set @colCAST = STUFF((select ',' +' CAST([' + c.name + '] AS numeric(7, 2)) AS [' + c.name + ']' FROM 
    sys.columns c 
    INNER JOIN 
    sys.types t ON c.user_type_id = t.user_type_id 
WHERE 
    c.object_id = OBJECT_ID('JRR_20170301_Stg') 
    and c.system_type_id = 108 for XML path('')),1,1, '') 

set @col = STUFF((select ',' +' [' + c.name + ']' FROM 
    sys.columns c 
    INNER JOIN 
    sys.types t ON c.user_type_id = t.user_type_id 
WHERE 
    c.object_id = OBJECT_ID('JRR_20170301_Stg') 
    and c.system_type_id = 108 for XML path('')),1,1, '') 

    select @col, @colCAST -- This returns the column name and good. 

--However, the problem starts from here below 
    declare @sql varchar(max) 

set @sql='SELECT max(col) 
FROM 
( 
SELECT ' + @colCAST + ' 
FROM JRR_20170301_Stg 
) s 
    unPIVOT (col for ListofColumns in ('+@col+')) as unpivat' 

    exec (@sql)