Within: INTERVAL, BETWEEN, DATESUB Urgh!

I should know this, but I am having a hell of a time with a query. Am I crazy?

Got a few records with these timestamps:
2013-02-04 20:12:49
2013-02-03 21:15:25
2013-02-03 20:25:11
2013-02-03 17:08:13
2013-02-03 16:31:18

I am trying to count how many records came in 20 minutes prior to 2013-02-03 21:15:25 (which should be zero)

SELECT COUNT(*) from xferleads where timestamp > '2013-02-03 21:15:25' - INTERVAL 20 MINUTE AND customer = 1

The interval just won't give me the right count. Even at one minute I get 2 counts on the above dataset.

Your query only looks for stuff where the timestamp is after 20:55. It says nothing about the timestamp also being before 21:15.


Note you can't (easily) use BETWEEN because you don't want to include the record at exactly timestamp=21:15.