Q:result of tquery 0 instead of 'nothing' ?

hi,

with the following statement i calculate the value TOTAL with a
tquery-component.

SELECT SUM(pcount + pextra) - (SELECT SUM(mcount) FROM minus WHERE MID
="1111")
AS Total FROM plus WHERE PID ="1111"

the problem is that it doesn't work when one of the tables (PLUS or
MINUS) don't have records
with related values. the result of the function SUM() is not 0 but
'nothing'. the whole calculation
goes wrong. is it possible to say the query that if there's nothing
found in SUM() the result should be
0 ?

i've tried to use the qbe component from the rxlibrary 2.32 because
ther's a property called
'BlankAsZero', but i cannot use it because i get the error
"column separators in the head of table area is missing"' (sorry, free
translation from german).

i get crazy about this problem. can anyone help me, please ?

thanks, tom