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.