Unpivot ALL Columns in a SQL Table

问题

I have a table with 30 columns and I want to easily unpivot ALL columns. I understand I can use this strategy:

SELECT col, value 
INTO New_Table
FROM
(SELECT * FROM Test_Data) p
UNPIVOT
(value FOR col IN (Column_Name1, Column_Name2... Column_Name30)) as unpvt

This is how my data comes in:

Column_Name1    Column_Name2    Column_Name3
Value11         Value21         Value31
Value12         Value22         Value32
Value13         Value23         Value33

This is how I want to store it in the new table:

New_Column1    New_cloumn2
Column_Name1   Value11
Column_Name1   Value12
Column_Name1   Value13
Column_Name2   Value21
...

But there must be an easier way than typing in the 30 column names.

Thanks in advance.

回答1:

This seems like a broken data model, but you can avoid typing out lists of columns.

You can use this to generate a list of columns:

SELECT name
FROM sys.columns
WHERE objecT_id = OBJECT_ID('Test_Data')

And:

DECLARE @List VARCHAR(MAX) = STUFF((SELECT DISTINCT ',' +   QUOTENAME(name)                     
                                    FROM sys.columns
                                    WHERE objecT_id = OBJECT_ID('Test_Data')                                    
                                    FOR XML PATH(''), TYPE).value('.', 'VARCHAR(MAX)') 
                                    ,1,1,'')
PRINT @List

You can then use that list in a dynamic sql statement:

DECLARE @List VARCHAR(MAX) = STUFF((SELECT DISTINCT ',' +   QUOTENAME(name)                     
                                    FROM sys.columns
                                    WHERE objecT_id = OBJECT_ID('Test_Data')                                    
                                    FOR XML PATH(''), TYPE).value('.', 'VARCHAR(MAX)') 
                                    ,1,1,'')
        ,@sql VARCHAR(MAX)
SET  @sql  =  'SELECT  col,value  
               INTO New_Table
               FROM  (SELECT  *  FROM  Test_Data)  p
               UNPIVOT (value  FOR  col  IN  ('+@List+'))  as  unpvt
              '
EXEC  (@sql)  

I suggest using PRINT (@sql) before using EXEC to ensure the dynamic query is what you were after.

来源：https://stackoverflow.com/questions/21996988/unpivot-all-columns-in-a-sql-table