There is no difference between a table and a table occurrence. But I understand why you want it and you can 1) simply print your list of tables by going to Define Database and (below) print or 2) specify a certain table occurrence to represent your 'base' table by the way you name it. Just be sure it begins with a character never used in any other table occurrence naming.
So, for instance, if you begin your 'base' tables as :customers, :invoices, :Products ... you can then easily identify which table you consider your base and they are easy to list and grab. A calcultion to find all base table could then be:
tables = TableNames ( Get ( FileName ) ) ;
n = PatternCount ( tables ; ":" )
LeftValues ( tables ; n )
) //end let