I am thinking about splitting one complex SELECT into two simple selects:

FOR SELECT id, ... FROM master_table WHERE ... DO
SELECT ... FROM detail_table WHERE master_id=:id

If the inner query uses prepared statements and proper indices, is it
reasonable to expect that it will perform about as fast as the more
complex original SELECT (one which would need to use multiple OR
conditions and at least some CASE statements, if not external functions,
in the WHERE section)?

Unfortunately I can't give an example because I don't have any real code
yet - I am thinking about possibilities at the moment. I just know the
single-statement version will be a lot more complex and probably won't
allow proper use of indices.

Pepak