Saturday, September 19, 2009

Pivoting SQL Data

So, the other day I was trying to pivot some SQL data that was basically in this format...

RecNumber ColNumber FieldName FieldValue
1 1 FirstName Davin
1 2 LastName Studer
2 1 FirstName Melissa
2 2 LastName Studer

I wanted to see it like this ...

RecNumber FirstName LastName
1 Davin Studer
2 Melissa Studer

It took me a while to figure out the syntax for this, but here it is. It uses the SQL pivot keyword.

This first portion dynamically creates the column names to be used in the pivot.

declare @cols varchar(max)

    select  @cols = stuff (
            select '], [' + FieldName
            from table
            group by FieldName
            order by min(ColNumber)
            xml path('')
        , 1, 2, ''
    ) + ']'

This next part creates a query within a string that we will run with the SQL exec command.

declare @query varchar(max)

    set @query = '
    select RecNumber, ' + @cols + '
    from (
        select RecNumber, FieldName, FieldValue
        from table
    ) dta
        for FieldName in (' + @cols + ')
    ) pvt'

All that is left to do is to execute the query that was created. I ended up putting this into a stored procedure.