SQL expression sometimes returning null instead of data

[JohnGa1]

I'm using the following SQL expression to fill a field in a report:

(select "inc_cat_1"."inc_cat_sc"
from "inc_cat"
as "inc_cat_1"
where "incident"."incident_id" = "act_reg"."incident_id"
and "act_reg"."cause_id" = "inc_cat_1"."inc_cat_id"
and "inc_cat_1"."inc_type" = 'c')

inc_cat_1 is an alias to table inc_cat. The annoying thing is that sometimes it returns the correct value and sometimes doesn't, returning null instead. Looking in the application the correct value is always there, but I can't see any reason why null would be returned.

 

[JohnGa1]

Sorry, forgot to mention, I'm running Crystal XI and SQL Server 2008.

 

[Madawc]

If you don't want nulls, test for them and exclude them.

Madawc Williams (East Anglia, UK). Using Crystal 11.5 with SQL and Windows XP

 

[CrystalProgDev]

Is it returning only one value or multiple values? If multiple, the first value will be displayed on the report if you have that in a section other than detail section.

 

[JohnGa1]

I'm doing some further investigating and will post. I assumed that more than one value would return an error, if this is not the case, then multiple values could be the problem.