Welcome to Subscribe On Youtube
Question
Formatted question description: https://leetcode.ca/all/1699.html
1699. Number of Calls Between Two Persons
SQL Schema
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).
Algorithm
- swap person1 and person2
- get by person1 < person2
- group by
Code
SQL
WITH caller as (
select from_id as person1, to_id as person2, duration
from Calls
UNION ALL
select to_id as person1, from_id as person2, duration
from Calls
),
unique_caller as (
select person1, person2, duration
from caller
where person1 < person2
)
select
person1, person2, count(*) as call_count, sum(duration) as total_duration
from unique_caller
group by person1, person2