Question

I asked this question in which I explained that I’m trying to get weekly point allocations from members of staff – including those that have allocated zero.

I have two tables:

Staff (140 rows) ID, Firstname, Surname, Position, Faculty, Subject, Hours, Allocation

Transactions (140,000 rows) Transaction_ID, Datetime, Giver_ID, Recipient_ID, Points, Category_ID, Reason

The SQL statement I’ve been trying is this:

SELECT
  CONCAT(s.Firstname, " ", s.Surname) AS `Staff Name`,
  COALESCE(SUM(t.Points), 0) AS `Points Allocated`
FROM staff s
LEFT JOIN transactions t ON t.Giver_ID = s.ID and t.Datetime >='2012-10-08'
GROUP BY s.ID
ORDER BY `Points Allocated` ASC

The query works as intended but it’s taking ~6 seconds to run.

The only index I have on either table is their Primary Keys.

The result of a EXPLAIN on this query states:

Sadly, I have no idea what that means! How can I go about optimising my query or tables to improve the run-time of this query?

Thanks in advance,

Answer 1

Have you tried simply adding an index key on the transaction.Giver_Id and also transaction.dateTime