Author: way0utwest

I wrote about a basic PIVOT query recently. It’s an interesting way to write a query and turn row data into columns. That’s handy, and lots of people have a need for it. However I’d never used PIVOT in production code. I’ve always written a crosstab query instead.

If I look back at the query I wrote, it looks like this:

select
    *
  from
    ( select
          team
        , opponent
        , teamscore
        from
          scores results
    ) as rawdata 

pivot

 ( avg(teamscore) for [Opponent] in ( [KC], [OAK], [SD] )

 ) as pivotresults;

This gives me these results:

team   KC   OAK  SD

DEN    31   35   24

However I could also write this query:

select 
    'team' = team
,   'KC' = sum( case when Opponent = 'KC' then TeamScore else 0 end) / 2
,   'OAK' = sum( case when Opponent = 'OAK' then TeamScore else 0 end) / 2
,   'SD' = sum( case when Opponent = 'SD' then TeamScore else 0 end) / 2
 from scores s
 where team = 'DEN'
 group by team

That gives me the same results.  The AVG item gets tricky as can don’t want zeros to be included in results. If there were a dynamic number of scores, I’d have to write a few subqueries to solve this issue.

Which one is more clear and easier to understand? That’s a good debate. However I will say that if I need to add a column, I think it’s easier to do so in the crosstab.

select 
    'team' = team
,   'KC' = sum( case when Opponent = 'KC' then TeamScore else 0 end) / 2
,   'OAK' = sum( case when Opponent = 'OAK' then TeamScore else 0 end) / 2
,   'SD' = sum( case when Opponent = 'SD' then TeamScore else 0 end) / 2
,   'NE' = sum( case when Opponent = 'NE' then TeamScore else 0 end)
 from scores s
 where team = 'DEN'
 group by team
;

Here’s the PIVOT:

 select
    *
  from
    ( select
          team
        , opponent
        , teamscore
        from
          scores results
    ) as rawdata
  pivot 
   ( avg(teamscore) for [Opponent] in ( [KC], [OAK], [SD], [NE] ) 
   ) as pivotresults;

I’ll also point out that Jeff Moden has written a few articles on this subject (Part 1 and Part 2) and his performance analysis shows that a crosstab performs better in almost all cases.

I wouldn’t recommend one over the other. You need to test them both at larger than expected data sets to determine which one works in your situation.