Question

I’m writing a query to summarize some data. I have a flag in the table that is basically boolean, so I need some sums and counts based on one value of it, and then the same thing for the other value, like so:

select    location   ,count(*)   ,sum(duration) from my.table where type = 'X'   and location = @location   and date(some_tstamp) = @date group by location 

And then the same for another value of the type column. If I join this table twice, how do I still group so I can only get aggregation for each table, i.e. count(a.*) instead of count(*)…

Would it be better to write two separate queries?

EDIT

Thanks everybody, but that’s not what I meant. I need to get a summary where type = ‘X’ and a summary where type = ‘Y’ separately…let me post a better example. What I meant was a query like this:

select    a.location   ,count(a.*)   ,sum(a.duration)   ,count(b.*)   ,sum(b.duration) from my.table a, my.table b where a.type = 'X'   and a.location = @location   and date(a.some_tstamp) = @date   and b.location = @location   and date(b.some_tstamp) = @date   and b.type = 'Y' group by a.location 

What do I need to group by? Also, DB2 doesn’t like count(a.*), it’s a syntax error.

Answer 1

  select    location   ,Sum(case when type = 'X' then 1 else 0 end) as xCount   ,Sum(case when type = 'Y' then 1 else 0 end) as YCount   ,Sum(case when type = 'X' then duration else 0 end) as xCountDuration   ,Sum(case when type = 'Y' then duration else 0 end) as YCountDuration from my.table where  location = @location   and date(some_tstamp) = @date group by location  

This should work in SQL Server. I guess db2 should have something similar.

Edit: Add a where condition to limit the records to select type = X or type = Y, if ‘type’ can have value other than X and Y.