Validation

#11

Yes, I've read the help as well, and indeed did so just prior to
posting. You'll note it doesn't actually come out and say that it
returns 0 when there is a relationship defined on tables that can be
found, fields that haven't been deleted, but no related records.

Quote:

The cCount has the disadvantage it does not return 0 when there are no
related records, but returns empty. (at least in my v8.5 adv). You have
to
build a wrapper to return a 1 or 0. I observed this some time ago and
even
built a testfile to recreate this.

Are you sure, in my experience count returns 0 when there are no
related records with only one exception: that its defined in a calc
field with "do not evaluate if all related fields are empty" (in which
case its blank)

Yes I am very sure. I have built a testfile. Create two tables with a
relation. Two related records and one not related.

For the related record
cCount < Number ; Count ( Related::rel) > returns 2
cIsempty < Number ; IsEmpty ( Related::rel) > returns 0 (False)
cIsvalid < Number ; IsValid ( Related::rel) > returns 1 (True)

For the not related record
cCount returns nothing (Empty)
cIsempty returns 1 (True)
cIsvalid returns 0 (False)

Actually cCount returns 0 for the not related record, unless I checked
off the do not evaluate if all referenced fields are empty. It did
this even if the calc was defined as a text field. (So it wasn't
simply converting 'empty' to 0.)

It only came back empty if it was set not to evaluate at all.

As for isValid I found that it worked as you said in my test db.

But I'm still not convinced, I'll swear IsValid has come back with a 1
even when there were no related records in real world databases I've
worked on, I can't create an example right now, but I was burnt by it
a couple times, which is why I never use it.

Quote:

I would not evaluate empty as "" but use the function IsEmpty

Fair enough. But can someone refresh my memory where the two
expressions yield different results? I seem to recall there actually
is a case...

(x = "") vs (IsEmpty(x))

When do they not evaluate the same?

Quote:

if ( IsEmpty ( count ( Related::rel ) ) ; 0 ; 1 )
which would return a 0 (False) when the relation returnd an empty count. And
although filemaker does evaluate an empty as false, I would prefer to see
something that can be evaluated. a 0 or False. Partly because I have people
who use my databases and sometimes want to change minor things. 0 or 1 I can
explain, but I fear an empty is a step to far. I already hear me explaining:
No an empty is not nothing, zero is nothing. But in this case the zero is a
false and not nothing...... No thanks.

I understand and even agree with your reasoning to coerce true-false
into the neat set of {1,0}. But Its a requirement strictly imposed by
you, not filemaker. FM is quite content to assign true or false to
arbitrary numbers and strings in a consistent and understandable way;
though perhaps perhaps not as understandable and simple as: (0=false,
1=true, there are no other cases)

cheers,
Dave

#12

Quote:

But can someone refresh my memory where the two
expressions yield different results? I seem to recall there actually
is a case...

(x = "") vs (IsEmpty(x))

===============

I don't know that, but I do know that a space in a field might visualy
evaluate as empty when actualy it is not.

There might technicaly be a difference between ="" and IsEmpty(x) but I
don't think Filemaker does care. But i'm interested if there might be such a
case, if only for my further knowledge of filemaker.

Further you are quite right when you stated: Actually cCount returns 0 for
the not related record, unless I checked
off the do not evaluate if all referenced fields are empty.

I just hadn't turned the checkbox off.

Keep well, Ursus

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Validation

comp.databases.filemaker comp.databases.filemaker

Re: Validation - 04-15-2007 , 06:50 PM

Re: Validation - 04-16-2007 , 03:48 AM