Number of Calls Between Two Persons 7-10-22

LINK --------   https://www.codingninjas.com/codestudio/problems/number-of-calls-between-two-persons_2181135?topList=top-100-sql-problems&leftPanelTab=0

Problem Statement

Table: Calls

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| from_id     | int     |
| to_id       | int     |
| duration    | int     |
+-------------+---------+
This table does not have a primary key, it may contain duplicates.
This table contains the duration of a phone call between from_id and to_id.
from_id != to_id


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).

------------------------------ solution 1 -----------------------------


SELECT 
    LEAST (from_id, to_id) person1 ,
    GREATEST(from_id,to_id) person2, 
    COUNT(*) call_count,
    SUM(duration) total_duration 
FROM calls
GROUP BY 1,2


-------------------------- solution 2 ------------------------


select  case   
    when from_id < to_id then from_id else to_id end as person1, 
    case when to_id > from_id then to_id else from_id end as person2, 
    count(*) as call_count,
    sum(duration) as total_duration 
from Calls 
group by  1, 2