A Brief Intro
Have you ever wondering how to count all the data and specific data with a certain condition on one query? If so, then this short post might be for you.
Let’s get started!
How?
Let’s say we organize an event and we store the participants data on our postgresql database.
Now we want to know all the participants that registered for the event and all the participants that actually attended the event. That means, even though someone register for the event, they might not attend the event.
With that in mind, we can use FILTER clause in our query like this:
SELECT
count(*) AS registered_participants,
count(*) FILTER (WHERE participants.status = 'attended') AS
attended_participants
FROM participants;
Alright, that’s it for now. See you next time!