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Exercise 12:1194.Tournament Winners

1.Description

Table: Players
+-------------+-------+
| Column Name | Type |
+-------------+-------+
| player_id | int |
| group_id | int |
+-------------+-------+
player_id is the primary key of this table.
Each row of this table indicates the group of each player
Table: Matches
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| match_id | int |
| first_player | int |
| second_player | int |
| first_score | int |
| second_score | int |
+---------------+---------+
- match_id is the primary key of this table.
- Each row is a record of a match, first_player and second_player
contain the player_id of each match.
- first_score and second_score contain the number of points of the first_player
and second_player respectively.
- You may assume that, in each match, players belongs to the same group.
​
The winner in each group is the player who scored the maximum total points within the group. In the case of a tie, the lowest player_id wins.
Write an SQL query to find the winner in each group.
The query result format is in the following example:
Players table:
+-----------+------------+
| player_id | group_id |
+-----------+------------+
| 15 | 1 |
| 25 | 1 |
| 30 | 1 |
| 45 | 1 |
| 10 | 2 |
| 35 | 2 |
| 50 | 2 |
| 20 | 3 |
| 40 | 3 |
+-----------+------------+
​
Matches table:
+------------+--------------+---------------+-------------+--------------+
| match_id | first_player | second_player | first_score | second_score |
+------------+--------------+---------------+-------------+--------------+
| 1 | 15 | 45 | 3 | 0 |
| 2 | 30 | 25 | 1 | 2 |
| 3 | 30 | 15 | 2 | 0 |
| 4 | 40 | 20 | 5 | 2 |
| 5 | 35 | 50 | 1 | 1 |
+------------+--------------+---------------+-------------+--------------+
​
Result table:
+-----------+------------+
| group_id | player_id |
+-----------+------------+
| 1 | 15 |
| 2 | 35 |
| 3 | 40 |
+-----------+------------+

2.Create Table and insert into values

create table if not exists leetcode.ex_1194_players
(player_id string ,group_id string) stored as orc ;
​
INSERT INTO table leetcode.ex_1194_players VALUES
('15', '1'),
('25', '1'),
('30', '1'),
('45', '1'),
('10', '2'),
('35', '2'),
('50', '2'),
('20', '3'),
('40', '3')
;
​
create table if not exists leetcode.ex_1194_matches
(match_id string,
first_player string,
second_player string,
first_score int,
second_score int
) stored as orc ;
​
INSERT INTO table leetcode.ex_1194_matches VALUES
('1', '15', '45', '3', '0'),
('2', '30', '25', '1', '2'),
('3', '30', '15', '2', '0'),
('4', '40', '20', '5', '2'),
('5', '35', '50', '1', '1')
This Problem test how to use UNION and Window Function, pay attention to the type of UNION.
​