To contain all 10 teams, each must play every other team at home and away. Can you write a query to do this?

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Assuming you have a table `teams` with a column `team_id`, you can generate all home‑away pairings with a self‑join and then union the reverse pairs. Example: ```sql -- List of teams SELECT team_id FROM teams; -- Generate home‑away pairs SELECT t1.team_id AS home_team, t2.team_id AS away_team FROM teams t1 JOIN teams t2 ON t1.team_id <> t2.team_id ORDER BY t1.team_id, t2.team_id; ``` This produces 10 × 9 = 90 rows. If you also need the reverse (away‑home) for each match, you can simply add the same query again or use a UNION ALL: ```sql SELECT t1.team_id AS home_team, t2.team_id AS away_team FROM teams t1 JOIN teams t2 ON t1.team_id <> t2.team_id UNION ALL SELECT t2.team_id AS home_team, t1.team_id AS away_team FROM teams t1 JOIN teams t2 ON t1.team_id <> t2.team_id; ``` Complexity is O(n²) where n is the number of teams. The query is straightforward and works in most SQL dialects.

To contain all 10 teams, each must play every other team at home and away. Can you write a query to do this?

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