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Editorial Team
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Asked: 2026-05-18T00:35:22+00:00

I’ve got a table with a lot (>20.000) records. It’s time to clean those

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I’ve got a table with a lot (>20.000) records.
It’s time to clean those up a little because queries are beginnen to take up a lot of recourses.
I have another (temporary) table with a recent records. All records in the first table that don’t exist in the second one can go.
However, I need to keep the id’s for the recent records because of some joins, so I can’t just TRUNCATE and then copy the table.
Is there any way yo do this?

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1 Answer

  1. Editorial Team
    DELETE FROM old_table WHERE id NOT IN (SELECT id FROM temp_table)

    Edit:
    id NOT IN (SELECT id FROM temp_table) is a lousy construction. If you have large tables and your server settings are tuned to low memory, you will execute this forever.

    @Piskvor‘s answer is a longer, but a much better query, that will work best on low-memory setups. And when I say “low memory”, I mean database servers that do not take up a full high-end computer, so pretty much any system that manages a small business website or stuff like that.

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