Elegant way to remove orphan rows?

Question

I have a table with a lot of history entries that contain customer IDs.

There is a separate customer table. Occasionally some of the customer entries are removed.

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Answer 1

DELETE h.* FROM history h
LEFT JOIN customer c ON h.customer_id = c.id
WHERE c.id IS NULL

I'm typing this from the top of my head, but you get the idea hopefully.

Delete syntax documentation