Question

This problem may seem like school work, but it isn’t. At best it is self-imposed school work. I encourage any teachers to take is as an example if they wish.

“First past the post” elections are single-round, meaning that whoever gets the most votes win, no second rounds.

Suppose a table for an election.

CREATE TABLE ElectionResults (
    DistrictHnd INTEGER NOT NULL,
    PartyHnd INTEGER NOT NULL,
    CandidateName VARCHAR2(100) NOT NULL,
    TotalVotes INTEGER NOT NULL,
    PRIMARY KEY DistrictHnd, PartyHnd);

The table has two foreign keys: DistrictHnd points to a District table (lists all the different electoral districts) and PartyHnd points to a Party table (lists all the different political parties). I won’t bother with other tables here, joining them is trivial. This is just a wee bit of context.

The question: What SQL query will return a table listing the DistrictHnd, PartyHnd, CandidateName and TotalVotes of the winners (max votes) in each District?

This does not suppose any particular database system. If you wish to stick to a particular implementation of SQL, go the way of SQLite and MySQL. If you can devise a better schema (or an easier one), that is acceptable too. Criteria: simplicity, portability to other databases.

Answer 1

Select DistrictHnd, PartyHnd, CandidateName, TotalVotes
From ElectionResults As ER
Where TotalVotes = (
                    Select Max(ER1.TotalVotes)
                    From ElectionResults As ER1
                    Where ER1.DistrictHnd = ER.DistrictHnd
                    )

In this query, if there is a tie (two people in the same district with the same number of total votes), they will both show.