Where is null AND something else

[simonb2013]

I had a working SA to count records where a field (iam_user) was null.

Count(distinct {$-<[iam_user]={"*"}>} rt_sch_obj)

Now I want to alter that, to say include 'AND flag=1'
So I did this : 

Count(distinct {$-<[iam_apex]={"*"}>*$<flag ={1}>} rt_sch_obj)

The results are now showing entries that I know have [iam_user] not null.

Getting really confused as to exactly what I'm doing.
Why is this not working as a logical and ?

What is the difference between :
$-<[iam_apex]={"*"}>
vs
$<[iam_apex]-={"*"}>

Lost  of previous questions relating to NULL situations, but can't find one around NULL AND.

Thanks for any help !!

[tresesco · Accepted solution]

You need a small trick here. 🙂 Try like:

Count(distinct {($-<[iam_apex]={"*"}>)*<flag ={1}>} rt_sch_obj)