Question

Well, I have two tables:

• events : id, title, description
• trip_events : id, event_id (points to events.id)

I need to select results from table named events.

SELECT *
FROM `events`

Simple as that, right?

The thing I need to achieve is that I need to select results from events, but exclude those rows that are in trip_events (if events.id != trip_events.event_id the excluded).

Here is example:

events:

• id : 5,
• id : 6,
• id : 7,
• id : 8;

trip_events:

• event_id : 6,
• event_id : 8;

With this data-set, only events with id as 5 and 6 would be returned.

How to do this?

I tried like this:

SELECT *
FROM `events`
JOIN `trip_events`
ON (`trip_events`.`event_id` = `events`.`id`)
WHERE `trip_events`.`event_id` != `events`.`id`

But it didn’t work.

Answer 1

select * from events where id not in
(select event_id from trip_events)

Edit:
As a side note, the ON condition can be thought of as a WHERE condition. The result of your query would be the same as the following

SELECT *
FROM `events`
JOIN `trip_events`
ON 1 = 1
WHERE (`trip_events`.`event_id`  = `events`.`id`)
AND   (`trip_events`.`event_id` != `events`.`id`)

Guess why you don’t get any results!