I was called by a team working on a new application to solve a mistery. Solved it... and walked away with this new one.
I'll change the names of the tables to make it easier to follow.

In the database there are these two tables MASTER with id as PK and DETAIL that links to MASTER through a field called idMASTER. No relations set anywhere nor RI nor triggers. Just plain vanilla tables.

They had made a form based on a MASTER table and given it mt_MASTER for alias (tha idea was that mt_ stood for main table). The DE had a cursor based on MASTER with mt_MASTER as an alias.

The RecordSource for a grid in the same form is based on a p-view on the table DETAIL. The default value for the idMaster column that links the two tables was set using DbSetProp() as MASTER.id. Note that it si not mt_MASTER, just the plain table name

Now, when run, the form complained because it could not find MASTER and so MASTER was added to the DE. And the form run ok. How is it possible?

Data is being retrived, deleted and saved correctly but it is mt_MASTER that controls the form and not the table added later. Nowhere in the form is MASTER on it's own referenced.

I've changed the form to get rid of the offending "mt_" prefix in the alias and all works as expected but the problem remains: why did it work before? What if there really was the need to have the same table opened 2 times in the DE for other reasons?.

TIA

Silvio