How to check if a field that points to a reference object has a value?

When you're creating a calculated attribute and want to get a value from a referent object, you need to check if the current record has a reference to this object at all - if a particular ID field has a value or not.

The recommended way to perform this validation is to check whether there is a referent object:

20  EQUAL REF:AdjustedDocument CONST:NULL        

and not whether the ID fields itself is empty:

20  EQUAL ATTRIB:AdjustedDocumentId CONST:NULL

The first approach is better because:

a. the second approach may lead to incorrect results - there are cases with wrong results when this approach is used in a SELECT clause or in multiple nested calculated attributes.

b. the first approach does not require type conversions - you're directly checking if there is a reference object and you don't have to use CAST or CONVERT operators to match the types before the comparison.