Problem Description –
Write an SQL query to report the number of calls and the total call duration between each pair of distinct persons (person1, person2)
where person1 < person2
.
Return the result table in any order.
The query result format is in the following example.

Problem Link – Calls between two persons
Difficulty Level – Medium
Solution –
SELECT
LEAST(from_id, to_id) as person1,
GREATEST(from_id, to_id) as person2,
COUNT(*) as call_count,
SUM(duration) as total_duration
FROM Calls
GROUP BY 1, 2