SQL query for Unpivot

[sds814]

I have a table structure (tblmapping) like the following:

TableName ColumnName ColumnValue
Product ProductID 1
Product ProductID 2
Product ProductName Keyboard
Product ProductName Mouse

I want to convert from column based data to row based data. I tried the following query, but syntax errors:

SELECT col,value
FROM
(SELECT DISTINCT ColumnName
FROM tblMapping
WHERE TableName = 'Product') p
UNPIVOT
(ColumnValue FOR ColumnName IN (SELECT DISTINCT ColumnName
								FROM tblMapping
								WHERE TableName = 'Product')
) AS unpvt;

Msg 156, Level 15, State 1, Line 7
Incorrect syntax near the keyword 'SELECT'.
Msg 102, Level 15, State 1, Line 9
Incorrect syntax near ')'.

Not sure what I'm doing wrong. Thanks for the help.