2339. All the Matches of the League

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LeetCode

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Problem

Table: Teams

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| team_name   | varchar |
+-------------+---------+
team_name is the primary key of this table.
Each row of this table shows the name of a team.

Write an SQL query that reports all the possible matches of the league. Note that every two teams play two matches with each other, with one team being the home_team once and the other time being the away_team.

Return the result table in any order.

The query result format is in the following example.

Example 1:

Input: 
Teams table:
+-------------+
| team_name   |
+-------------+
| Leetcode FC |
| Ahly SC     |
| Real Madrid |
+-------------+
Output: 
+-------------+-------------+
| home_team   | away_team   |
+-------------+-------------+
| Real Madrid | Leetcode FC |
| Real Madrid | Ahly SC     |
| Leetcode FC | Real Madrid |
| Leetcode FC | Ahly SC     |
| Ahly SC     | Real Madrid |
| Ahly SC     | Leetcode FC |
+-------------+-------------+
Explanation: All the matches of the league are shown in the table.

Code

SELECT a.team_name home_team, b.team_name away_team
FROM Teams a JOIN Teams b
ON a.team_name != b.team_name;