Number of Calls Between Two Persons

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:

Calls table:
+---------+-------+----------+
| from_id | to_id | duration |
+---------+-------+----------+
| 1       | 2     | 59       |
| 2       | 1     | 11       |
| 1       | 3     | 20       |
| 3       | 4     | 100      |
| 3       | 4     | 200      |
| 3       | 4     | 200      |
| 4       | 3     | 499      |
+---------+-------+----------+

Result table:
+---------+---------+------------+----------------+
| person1 | person2 | call_count | total_duration |
+---------+---------+------------+----------------+
| 1       | 2       | 2          | 70             |
| 1       | 3       | 1          | 20             |
| 3       | 4       | 4          | 999            |
+---------+---------+------------+----------------+

Users 1 and 2 had 2 calls and the total duration is 70 (59 + 11).
Users 1 and 3 had 1 call and the total duration is 20.
Users 3 and 4 had 4 calls and the total duration is 999 (100 + 200 + 200 + 499).



Answer:

WITH CALL_LOGS AS (
    SELECT FROM_ID,
           TO_ID,
           DURATION
    FROM CALLS

    UNION ALL

    SELECT TO_ID,
           FROM_ID,
           DURATION
    FROM CALLS
)


SELECT FROM_ID AS PERSON1,
       TO_ID AS PERSON2,
       COUNT(*) AS CALL_COUNT,
       SUM(DURATION) AS TOTAL_DURATION
FROM CALL_LOGS
WHERE FROM_ID < TO_ID
GROUP BY FROM_ID, TO_ID
;