Top Travellers 17-10-22

link ----  https://www.codingninjas.com/codestudio/problems/top-travellers_2117112?topList=top-100-sql-problems


Problem Statement

Table: Users

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| id            | int     |
| name          | varchar |
+---------------+---------+
id is the primary key for this table.
name is the name of the user.


Table: Rides

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| id            | int     |
| user_id       | int     |
| distance      | int     |
+---------------+---------+
id is the primary key for this table.
user_id is the id of the user who travelled the distance "distance".


Write an SQL query to report the distance travelled by each user.

Return the result table ordered by travelled_distance in descending order, if two or more users travelled the same distance, order them by their name in ascending order.

The query result format is in the following example.



Users table:
+------+-----------+
| id   | name      |
+------+-----------+
| 1    | Alice     |
| 2    | Bob       |
| 3    | Alex      |
| 4    | Donald    |
| 7    | Lee       |
| 13   | Jonathan  |
| 19   | Elvis     |
+------+-----------+

Rides table:
+------+----------+----------+
| id   | user_id  | distance |
+------+----------+----------+
| 1    | 1        | 120      |
| 2    | 2        | 317      |
| 3    | 3        | 222      |
| 4    | 7        | 100      |
| 5    | 13       | 312      |
| 6    | 19       | 50       |
| 7    | 7        | 120      |
| 8    | 19       | 400      |
| 9    | 7        | 230      |
+------+----------+----------+

Result table:
+----------+--------------------+
| name     | travelled_distance |
+----------+--------------------+
| Elvis    | 450                |
| Lee      | 450                |
| Bob      | 317                |
| Jonathan | 312                |
| Alex     | 222                |
| Alice    | 120                |
| Donald   | 0                  |
+----------+--------------------+
Elvis and Lee travelled 450 miles, Elvis is the top traveller as his name is alphabetically smaller than Lee.
Bob, Jonathan, Alex and Alice have only one ride and we just order them by the total distances of the ride.
Donald didn't have any rides, the distance travelled by him is 0.


---------------------- solution -------------------------

select t1.name , coalesce (sum(t2.distance),0) travelled_distance

from users t1 left 
join rides t2 
on t1.id = t2.user_id
group by 1
order by 2 desc,1

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



SELECT u.name AS name, COALESCE(SUM(r.distance),0) AS travelled_distance
FROM Users u LEFT JOIN Rides r
ON u.id = r.user_id
GROUP BY u.name
ORDER BY travelled_distance DESC, u.name;