Checking if new interval overlaps - MySQL (or PHP)

Question

I\'ve been thinking on how I can simplify the problem presented here. Complex MySQL Query - Checking for overlapping DATE intervals

At it\'s heart, minus all the fa

Answer 1

You can phrase an insert as:

insert into schedules(start, end)
    select s, e
    from (select $start s, $end as e) t
    where not exists (select 1
                      from schedules s2
                      where s.start <= t.end and s.end >= t.start
                     );

This will only insert the value if it doesn't overlap with an existing row in the table.

Answer 2

Using folowing abbreviations:

• [old] := existing range
• [new] := inserting range
• OS := (old) existing_range.start
• OE := (old) existing_range.end
• NS := (new) inserting_range.start
• NE := (new) inserting_range.end

the condition for overlaping of two ranges (old and new) is: (OS < NE) AND (OE > NS)

While the solution might be not trivial, its not that difficult to get there:

There is no overlaping if the new range is completly before or after the existing range: [new] <= [old] OR [old] <= [new] and that means that:

(NE <= OS) OR (OE <= NS)

Negotiating this statement we get the condition for overlaping:

!( (NE <= OS) OR (OE <= NS) )

Now using De Morgan's law we can write it as

!(NE <= OS) AND !(OE <= NS)

And this is equivalent to

(NE > OS) AND (OE > NS)

wich can be rewriten as

(OS < NE) AND (OE > NS)

Now we can find all overlaping ranges using

SELECT o.*
FROM Schedules o
WHERE o.start < :new_end
  AND o.end   > :new_start