Instead of using EXISTS I prefer to use LEFT JOIN, which gave you ALL records from 'Main Table' and only these from joined table which match the join condition. When I tested for IS NULL that means that I want only these records from 'Main Table' which didn't have analog in joined table.
Against Stupidity the Gods themselves Contend in Vain - Johann Christoph Friedrich von Schiller
The only thing normal about database guys is their tables.