1212. Team Scores in Football Tournament 🔒

Description

Table: Teams

+---------------+----------+
| Column Name   | Type     |
+---------------+----------+
| team_id       | int      |
| team_name     | varchar  |
+---------------+----------+
team_id is the column with unique values of this table.
Each row of this table represents a single football team.

 

Table: Matches

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| match_id      | int     |
| host_team     | int     |
| guest_team    | int     | 
| host_goals    | int     |
| guest_goals   | int     |
+---------------+---------+
match_id is the column of unique values of this table.
Each row is a record of a finished match between two different teams. 
Teams host_team and guest_team are represented by their IDs in the Teams table (team_id), and they scored host_goals and guest_goals goals, respectively.

 

You would like to compute the scores of all teams after all matches. Points are awarded as follows:

• A team receives three points if they win a match (i.e., Scored more goals than the opponent team).
• A team receives one point if they draw a match (i.e., Scored the same number of goals as the opponent team).
• A team receives no points if they lose a match (i.e., Scored fewer goals than the opponent team).

Write a solution that selects the team_id, team_name and num_points of each team in the tournament after all described matches.

Return the result table ordered by num_points in decreasing order. In case of a tie, order the records by team_id in increasing order.

The result format is in the following example.

 

Example 1:

Input: 
Teams table:
+-----------+--------------+
| team_id   | team_name    |
+-----------+--------------+
| 10        | Leetcode FC  |
| 20        | NewYork FC   |
| 30        | Atlanta FC   |
| 40        | Chicago FC   |
| 50        | Toronto FC   |
+-----------+--------------+
Matches table:
+------------+--------------+---------------+-------------+--------------+
| match_id   | host_team    | guest_team    | host_goals  | guest_goals  |
+------------+--------------+---------------+-------------+--------------+
| 1          | 10           | 20            | 3           | 0            |
| 2          | 30           | 10            | 2           | 2            |
| 3          | 10           | 50            | 5           | 1            |
| 4          | 20           | 30            | 1           | 0            |
| 5          | 50           | 30            | 1           | 0            |
+------------+--------------+---------------+-------------+--------------+
Output: 
+------------+--------------+---------------+
| team_id    | team_name    | num_points    |
+------------+--------------+---------------+
| 10         | Leetcode FC  | 7             |
| 20         | NewYork FC   | 3             |
| 50         | Toronto FC   | 3             |
| 30         | Atlanta FC   | 1             |
| 40         | Chicago FC   | 0             |
+------------+--------------+---------------+

Solutions

Solution 1: Left Join + Group By + Case Expression

We can join the Teams table and the Matches table using a left join, where the join condition is team_id = host_team OR team_id = guest_team, to obtain all the match information for each team.

Next, we group by team_id and use a CASE expression to calculate the points for each team according to the following rules:

• If the team is the host team and has more goals than the guest team, add \(3\) points to the team's score.
• If the team is the guest team and has more goals than the host team, add \(3\) points to the team's score.
• If the host team and the guest team have the same number of goals, add \(1\) point to the team's score.

Finally, we sort the result by points in descending order, and if the points are the same, we sort by team_id in ascending order.

MySQL

# Write your MySQL query statement below
SELECT
    team_id,
    team_name,
    SUM(
        CASE
            WHEN team_id = host_team
            AND host_goals > guest_goals THEN 3
            WHEN team_id = guest_team
            AND guest_goals > host_goals THEN 3
            WHEN host_goals = guest_goals THEN 1
            ELSE 0
        END
    ) AS num_points
FROM
    Teams
    LEFT JOIN Matches ON team_id = host_team OR team_id = guest_team
GROUP BY 1
ORDER BY 3 DESC, 1;

Comments