Question

I’ve got the next problem up from this one: Comparing date ranges

The solution to comparing two ranges is the query:

SELECT * FROM periods WHERE NOT (range_start > @check_period_end OR range_end < @check_period_start)

I have the added problem. I am allowing people to enter a range of periods. To be precise they enter a duration (i.e 1 week) and a range of start dates (i.e. first 2 weeks in may) and I have to find out if there is a one week slot in the range they specified.

The naive solution is to run the above query for every day in my range. So – to check for 3 days slots in a month range I’d have to run 30 queries. Is there a more efficient way?

For bonus points – I am using Django. Is there a good solution using the Django ORM?

Edit – In an effort to simplify the question I think I’ve turned it into a different question! My actual problem is to find ‘free gaps’. I think this invalidates some of the ‘pure SQL’ approaches below. I thought it would be sensible to start a new question rather than muddling this one. Others are likely to find this question useful in it’s current form.

Answer 1

The problem is simpler than it may seem at first glance, as the user is not directly specifying an end date in their criteria.

SELECT * FROM periods p WHERE p.range_start >= @min_start AND   p.range_start <= @max_start AND   DATE_ADD(p.range_start, INTERVAL @duration DAY) <= p.range_end