SQL Count days till first of the month

How would I count the days from a date till the first of the following month

Example:

--Start Date
07-07-2011

How many days till:

-- The 1st of the succeeding month of the start date above
08-01-2011

Expected Result (in days):

25

So if I counted the day I get 25, so running this query 开发者_开发问答gets me the desired timestamp:

SELECT CURRENT_DATE + INTERVAL '25 DAYS'

Results:

2011-08-01 00:00:00

just can't think of a way to get the number of days, any suggestions?

Or start date, end date, number of days between?

I don't have a PostgreSQL server handy, so this is untested, but I would try:

SELECT (DATE_TRUNC('month', CURRENT_DATE) + INTERVAL '1 MONTH') - CURRENT_DATE