INSERT INTO .. VALUES () LIMIT 1
Doesn’t exist. Hopefully you know how many VALUES() you put in there!
INSERT INTO .. SELECT ... LIMIT 1
Does exist and is pretty useful, and off topic since the LIMIT is on the SELECT.
DELETE ... LIMIT 1
UPDATE ... LIMIT 1
Extremely rarely useful. Either you know your database enough to be certain that your WHERE matches a UNIQUE condition, or you don’t, in which case you should spend a little more time looking at your database and learning SQL.
But …
UPDATE jobs SET owner=me WHERE owner IS NULL ORDER BY job_submit_time LIMIT 1
Can be extremely useful! This makes a near-lockless job queue, where you can come and take a job from the queue without any waiting, locking, or conflict resolution. Quite excellent.
DELETE FROM cache ORDER BY last_update_time LIMIT N
Cache takes too much space ? Purge the N oldest rows…