How to separate positive and negative numbers into their own columns?

Question

I have a table with the following columns and data:

activity_dt | activity_amt
 2009-01-01 |   -500
 2009-01-01 |    750

Can I write a query that looks at the sign of activity_amt and puts it in the credits column if it's positive, and the debits column if it's negative? (I'm using Sybase)

activity_dt | debits | credits
 2009-01-01 |  -500  |   750

Answer 1

select activity_dt, 
    sum(case when activity_amt < 0 then activity_amt else 0 end) as debits, 
    sum(case when activity_amt > 0 then activity_amt else 0 end) as credits
from the_table
group by activity_dt
order by activity_dt