Suppose you want to get a record from database which returns a large amount of data and requires multiple joins.
So my question would be, is it better to use a single query to check if data exists and get the result if it exists? Or do a more simple query to check if data exists then id record exists, query once again to get the result knowing that it exists.
Example:
3 tables a, b and ab(junction table)
select * from
from a, b, ab
where condition
and condition
and condition
and condition etc...
or
select id
from a, b ab
where condition
then if exists do the query above.
So I don't know if there is any reason to do the second. Any ideas how this affects DB performance or does it matter at all?