Dynamic SQL to generate column names?

Question

I have a query where I\'m trying pivot row values into column names and currently I\'m using SUM(Case...) As \'ColumnName\' statements, like so:

Answer 1

Why do this using hard coded column names when you can pull all this dynamically from any table?

Using UNPIVOT and COALESCE, I can dynamically pull a list of columns from any table and associated column values for any record in a record listing and combine them in a list of column names with values by row. Here is the code. Just drop in your database and table name. The column/value table will be generated for you in SQL Server. Keep in mind, to get a shared column of values for the columns you want to convert to sql variant or text strings. But a great way to get a sample column list of values with matching column names and types with our while loops or cursors. Its pretty fast:

-- First get a list of all known columns in your database, dynamically...
DECLARE @COLUMNS nvarchar(max)
SELECT @COLUMNS = 

CASE
 WHEN A.DATA_TYPE = 'nvarchar' OR A.DATA_TYPE = 'ntext' THEN 
COALESCE(@COLUMNS + ',','') + 'CAST(CONVERT(nvarchar(4000),['+A.[name]+']) AS sql_variant) AS ['+A.[name]+']'
 WHEN A.DATA_TYPE = 'datetime' OR A.DATA_TYPE = 'smalldatetime' THEN 
COALESCE(@COLUMNS + ',','') + 'CAST(CONVERT(nvarchar,['+A.[name]+'],101) AS sql_variant) AS ['+A.[name]+']'
 ELSE
 COALESCE(@COLUMNS + ',','') + 'CAST(['+A.[name]+'] AS sql_variant) AS ['+A.[name]+']'
 END

FROM
(
 SELECT
 A.name,
 C.DATA_TYPE
 FROM YOURDATABASENAME.dbo.syscolumns A
 INNER JOIN YOURDATABASENAME.dbo.sysobjects B ON B.id = A.id
 LEFT JOIN
 (
 SELECT 
COLUMN_NAME,
 DATA_TYPE
 FROM YOURDATABASENAME.INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = 'YOURTABLENAME' 
) C ON C.COLUMN_NAME = A.name
 WHERE B.name = 'YOURTABLENAME'
 AND C.DATA_TYPE <> 'timestamp' 
) A
-- Test that the formatted columns list is returned...
--SELECT @COLUMNS

-- This gets a second string list of all known columns in your database, dynamically...
DECLARE @COLUMNS2 nvarchar(max)
SELECT @COLUMNS2 = COALESCE(@COLUMNS2 + ',','') + '['+A.[name]+']'
FROM
(
 SELECT
 A.name,
 C.DATA_TYPE
 FROM YOURDATABASENAME.dbo.syscolumns A
 INNER JOIN YOURDATABASENAME.dbo.sysobjects B ON B.id = A.id
 LEFT JOIN
 (
 SELECT 
COLUMN_NAME,
 DATA_TYPE
 FROM YOURDATABASENAME.INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = 'YOURTABLENAME' 
) C ON C.COLUMN_NAME = A.name
 WHERE B.name = 'YOURTABLENAME'
 AND C.DATA_TYPE <> 'timestamp' 
) A
-- Test that the formatted columns list is returned...
--SELECT @COLUMNS2


-- Now plug in the list of the dynamic columns list into an UNPIVOT to get a Column Name / Column Value list table...
DECLARE @sql nvarchar(max)
SET @sql = 
'
SELECT
ColumnName,ColumnValue
FROM
(
SELECT
'+@COLUMNS+'
FROM YOURDATABASENAME.dbo.YOURTABLENAME  
WHERE CHANGE_ID IN (SELECT ChangeId FROM YOURDATABASENAME.dbo.OperatorProcess WHERE OperatorProcessID = 3)
) AS SourceTable
UNPIVOT
(
ColumnValue FOR ColumnName IN ('+@COLUMNS2+')
) AS PivotTable
'

EXEC (@sql)