Problem

Given a table of data with three columns: id, start, and end, write a SQL query to find all pairs of rows where the start and end times overlap.
Example input:
id | start | end
1 | 10 | 20
2 | 15 | 30
3 | 25 | 35
4 | 45 | 55
Example output:
1, 2
2, 3

Solution

SELECT t1.id, t2.id
FROM table t1
JOIN table t2
ON t1.start < t2.end AND t1.end > t2.start
WHERE t1.id < t2.id;

/*

The solution above is optimal because it uses a JOIN to find all pairs of rows that overlap.

*/