Question

In MySQL, If I have a list of date ranges (range-start and range-end). e.g.

10/06/1983 to 14/06/1983 15/07/1983 to 16/07/1983 18/07/1983 to 18/07/1983 

And I want to check if another date range contains ANY of the ranges already in the list, how would I do that?

e.g.

06/06/1983 to 18/06/1983 = IN LIST 10/06/1983 to 11/06/1983 = IN LIST 14/07/1983 to 14/07/1983 = NOT IN LIST 

Answer 1

This is a classical problem, and it’s actually easier if you reverse the logic.

Let me give you an example.

I’ll post one period of time here, and all the different variations of other periods that overlap in some way.

           |-------------------|          compare to this one                |---------|                contained within            |----------|                   contained within, equal start                    |-----------|          contained within, equal end            |-------------------|          contained within, equal start+end      |------------|                       not fully contained, overlaps start                    |---------------|      not fully contained, overlaps end      |-------------------------|          overlaps start, bigger            |-----------------------|      overlaps end, bigger      |------------------------------|     overlaps entire period 

on the other hand, let me post all those that doesn’t overlap:

           |-------------------|          compare to this one      |---|                                ends before                                  |---|    starts after 

So if you simple reduce the comparison to:

starts after end ends before start 

then you’ll find all those that doesn’t overlap, and then you’ll find all the non-matching periods.

For your final NOT IN LIST example, you can see that it matches those two rules.

You will need to decide wether the following periods are IN or OUTSIDE your ranges:

           |-------------|    |-------|                       equal end with start of comparison period                          |-----|   equal start with end of comparison period 

If your table has columns called range_end and range_start, here’s some simple SQL to retrieve all the matching rows:

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

Note the NOT in there. Since the two simple rules finds all the non-matching rows, a simple NOT will reverse it to say: if it’s not one of the non-matching rows, it has to be one of the matching ones.

Applying simple reversal logic here to get rid of the NOT and you’ll end up with:

SELECT * FROM periods WHERE range_start <= @check_period_end       AND range_end >= @check_period_start