Specifying the unique key columns – PB Docs 2019

The Unique Key Columns box in the Specify Update Properties dialog
box specifies which columns PowerBuilder uses to identify a row being
updated. PowerBuilder uses the column or columns you specify here as the
key columns when generating the WHERE clause to update the database (as
described below):

The key columns you select here must uniquely identify a row in
the table. They can be the table’s primary key, though they don’t have
to be.