This is part of the Semicolon&Sons Code Diary - consisting of lessons learned on the job. You're in the databases category.
Last Updated: 2024-04-25
How to get records A (say station_location) that have at least 1 of record B
associated (say slots).
The trick is to use a subquery that references the parent query:
SELECT * FROM `station_locations`
WHERE EXISTS (
SELECT *
FROM `slots`
WHERE `station_locations`.`id` =
`slots`.`station_location_id`
)