Storing negative numbers

[newbi]

I have data with type and amount columns.  Wheres type can be debit or credit.  Depanding on type i would to store the amount in positive or negative.

If the type is credit then i would like to store amount value in negative  "-1000" else positive.

Also, is it good idea to store the negative values in table or to calculate the values at query level for reporting ?

Thanks

[SASPhile]

data have;

input type $1-7  amount;

cards;

credit  1000

debit   2000

unknown 3000

;

run;

data want;

set have;

if upcase(type) eq 'CREDIT' then amount=0-amount;

else amount=amount;

run;