Dynamic SQL Server Pivot ( UNPIVOT ) column name to a row value

Question

I\'m using SQL Server. I have a query that returns 1 row of data.

SELECT *
FROM DBO.MY_TABLE
WHERE ID = 5

It will look something like this:

Answer 1

So you have a couple problems... the first is that this requires dynamic sql because the table and columns are not known ahead of time so you can't just use a simple unpivot.

That also means that you'll have to get the column names from system tables.

Your second problem is that all your datatypes are unknown so you have to cast all the columns to something that can support everything and any length... varchar(max).

So, with those two obstacles in mind here is a solution:

declare @yourTable varchar(50)
declare @yourKeyField varchar(50)
declare @yourKey varchar(50)

set @yourTable = 'MyTable' /** change to tablename or pass as parameter */
set @yourKeyField = 'ID'   /** change to fieldname or pass as parameter */
set @yourKey = '5'         /** change to key value or pass as parameter */

declare @query nvarchar(max)  

select @query = COALESCE(@query+' union all ','') + 'select ''' + c.name + ''' as
[Column], Cast([' + c.name + '] AS VarChar(MAX)) as [Value] from ' + @yourTable + ' 
where ' + @yourKeyField + ' = ''' + @yourKey + '''' from syscolumns c 
    inner join sysobjects o on c.id = o.id and o.xtype = 'u'
    where o.name = @yourTable order by c.colid

exec sp_executesql @query /** execute query */

Finally, I can't in good conscience recommend a solution that uses dynamic sql without warning of the dangers involved in such (from both a performance standpoint and the potential for injection). Read this excellent article if you want to increase your knowledge on the subject.

http://www.sommarskog.se/dynamic_sql.html