MySQL simple update (value - var = new value)

[knowj]

Is it possible to update a field with its current value minus a figure (1 for instance) within 1 query or would i need to query the database with a select to get the value then minus the value and UPDATE

basically:

SELECT stock FROM sizes WHERE id= '1'
UPDATE sizes SET stock='".($stock - 1)."' WHERE id='1'

Would this type of thing be possible within a single query?

thanks in advance
john

[laserlight]

You should be able to run:

UPDATE sizes SET stock=stock-1 WHERE id=1