T-SQL sum on decimal results in integer

Question

Alright, T-SQL isn't acting as I would expect. Look at this:

SELECT SUM(DEBET),SUM(CREDIT)
CONVERT(DECIMAL(9,2),
    CASE WHEN SUM(DEBET) - SUM(CREDIT) > 0.00
        THEN CONVERT(DECIMAL(9,2),SUM(CONVERT(DECIMAL(9,2),DEBET))) - CONVERT(DECIMAL(9,2),SUM(CONVERT(DECIMAL(9,2),CREDIT)))
        ELSE CONVERT(DECIMAL(9,2),0.00)
    END
) AS DEBETSALDO
FROM OTHERTABLE

DEBET and CREDIT in OTHERTABLE both are of type decimal; DEBET(decimal,null) according to the tooltip.

The result is...

DEBET      CREDIT  DEBETSALDO
6817.07    0.00    0

Why and where, if DEBET and CREDIT are interpreted as decimals, does SQL convert my whole shebang back to integer in this select statement? Maybe add a few more converters?

EDIT

I just changed

SELECT DEBET, CREDIT

into

SELECT SUM(DEBET), SUM(CREDIT)

To emphasize where the problem lies. The results stay the same.

Answer 1

Found it.

Apparently when you convert a decimal(11,2) to a decimal(9,2) leads to precision loss.

Sorry, I should have double checked that. But nevertheless, 6817.07 should fit inside decimal(9,2), right?

Thanks for the help.