the select statement starts with a paranthed OR statement. In that OR statement as soon as a condition is met it evaluates to TRUE and moves to the next part of the select statement (the AND startdate part).

so when a user selects "ALL" in your param

{?PartNbr} = 'All'  is a true statement which ends the OR. but it does not actually filter your data which is the same thing as selecting all records (but more efficient because it does not have to evaluate each row).

Since the OR statement ended it will now apply your date range criteria.

Does that help?

 

If {?Agent}='ALL' Then true Else {Command.AGENT} = {?Agent}

true works as well. use it all the time.