Question

many user can create many Events. And users can send request to owner to participate in that event(as candidate, voter or both). When it’s a candidate request then additional details are stored in candidate details table.

User(u_id pk, username, password)

Event(e_id pk,u_id,e_name,e_date)

UserRequestPool(urp_id pk,u_id,e_id,request_type)#adding 2 entries if request type is both

CandidateDetails(id pk,u_id,e_id,candidate_image,candidate_promises)

Ballot(u_id,e_id,flag) #to ensure duplicate voting

Answer 1

You should store the user request pool id in the candidate details instead of the event id and user id:

CandidateDetails (id pk, urp_id, candidate_image, candidate_promises)

Same for the ballot table:

Ballot (urp_id, flag)

You might want to store the request types in a table:

UserRequestPool (urp_id pk, u_id, e_id, r_id)

RequestType (r_id, request_type)