mySQL Quickly Delete Lots of Rows

I have two tables, I need all rows from the first that don't appear in the second.

The tables can be destroyed as they're dumps from other tables.

First table has ~57million rows开发者_如何学Python. Second table has ~10million rows.

Both of these queries are taking forever for obvious reasons, please help me do this quicker.

SELECT *
FROM db.first
WHERE id NOT IN (SELECT id FROM db.second)

DELETE FROM db.first
WHERE id IN (SELECT id FROM db.second)

Edit: I don't need any records from the second table, I only need rows that appear in the first table that don't appear in the second table.

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It would probably be a lot quicker using joins:

select one.*
from db.first one
left join db.second two on one.id = two.id
where two.id is null

and the delete:

delete first
from first 
join second on first.id = second.id