I have three tables 'events', 'event_participants' & 'participant_work_submissions'.
Event table stores different events.
Event_participants table stores participants participating in different events.
Participant_work_submissions table stores work submitted by participants in different events.
I hope I explained my question properly, but even though if some one have any question, please ask, I will explain it.
Looking for response.
I am also trying to figure out the solution: Before I insert new record I can fire query to get the number of works submitted(count) to that event.
While inserting the record I will count+1 in the 'work_sequence_number' column.
But while doing this if some other user submitted his/her work then it would be difficult to resolve to whom I assign that number.