SQL Count() question

Question

I have a table with a charge/credit column:

Item | PriceVal | CostVal | CHARGE_CODE

1        5             3         CH

2        8             5         CH

1        -5            -3        CR

3        7             1         CH

4        15            10        CH

1        5             3         CH

I've got the query I need to get the NET price and cost, but I'm also interested in the NET charges. Right now I have:

SELECT Item, SUM(PriceVal), SUM(CostVal) FROM Table GROUP BY Item

How do I get another column with the value COUNT(SUM(CHARGE_CODE=CH)-SUM(CHARGE_CODE=CR)).

I'm at a loss.

Answer 1

count() is going to count one for every value thats not null, so I don't think thats exactly what you want. Take the count out and just take the

sum(case when charge_code = CH then costval else 0 end) 
- sum(case when charge_code = 'CR' then costval else 0 end)

Answer 2

Not 100% sure what you want, but you can count only certain rows like this:

SELECT COUNT(IF(CHARGE_CODE=CH,1,NULL)) ...

And similarly sum certain values from certain rows like this:

SELECT SUM(IF(CHARGE_CODE=CH,PriceVal,0)) ...

Answer 3

Since you have the dollar values entered as negatives in the table already, you can use the simple formula:

select
    Item,
    sum(PriceVal),
    sum(CostVal),
    sum(PriceVal-CostVal)
from Table
group by Item

I don't believe you should be subtracting the credit items as they're already negative.

If you really do want want the net count of transactions:

select
    Item,
    sum(PriceVal),
    sum(CostVal),
    sum(case when charge_code = 'CH' then 1 else 0 end) -
        sum(case when charge_code = 'CR' then -1 else 0 end)
from Table
group by Item

or, if there are only two charge codes, substitute:

sum(case when charge_code = 'CH' then 1 else -1 end)

for the last column.