MySQL efficient join with "in" without duplicates - mysql

Question

I have an event table
+----------+------------+
| event_id | event_name |
+----------+------------+
| 1 | event1 |
| 2 | event2 |
| 3 | event3 |
| 4 | event4 |
+----------+------------+
And an event_performer table
+--------------------+----------+--------------+
| event_performer_id | event_id | performer_id |
+--------------------+----------+--------------+
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 2 | 1 |
| 4 | 2 | 2 |
| 5 | 3 | 3 |
| 6 | 3 | 4 |
| 7 | 4 | 3 |
| 8 | 4 | 4 |
+--------------------+----------+--------------+
I want to get all the events with performer ids 1 and 2, so I run the following query:
select event.* from event
join event_performer
on event.event_id = event_performer.event_id
and performer_id in (1,2)
order by event_name
When I do that, I obviously get duplicate events (two for event_id 1 and two for event_id 2). What's the most efficient way in MySQL remove the duplicates so that I get each event record once?
One idea is to use select distinct event.* How efficient is that for a large number of fields and records?
Note that the example tables are oversimplified. Each table has MANY more fields and MANY more records.

Answer 1

You can try to use Group BY
select event.event_id, event.event_name from event
join event_performer
on event.event_id = event_performer.event_id
and performer_id in (1,2)
GROUP BY event_name, event.event_id
order by event_name
However do note that if you have created an index on your column then using GROUP BY is similar to using DISTINCT. But if you have not created an index then I would recommend you to go with using DISTINCT as it is comparatively faster than GROUP BY.