Question

I have a database with 1000 records.
I am trying to create an SQL statement so if the number of records grows above 1000, then the oldest records are deleted (i.e. the new records above 1000 ‘replace’ the oldest records).
I am using SQLite, but I assume the usual SQL syntax will fit here.

Answer 1

If you use an auto-increment field, you can easily write this to delete the oldest 100 records:

DELETE FROM mytable WHERE id IN (SELECT id FROM mytable ORDER BY id ASC LIMIT 100)

Or, if no such field is present, use ROWID:

DELETE FROM mytable WHERE ROWID IN (SELECT ROWID FROM mytable ORDER BY ROWID ASC LIMIT 100)

Or, to leave only the latest 1000 records:

DELETE FROM mytable WHERE ROWID IN (SELECT ROWID FROM mytable ORDER BY ROWID DESC LIMIT -1 OFFSET 1000)