Question

我很惭愧地说我的SQL体验很少被使用，当我必须构建一个稍微复杂的查询时，它就会失败，所以我很感激SQL专家的建议。

基本上我有两个表，类似于以下

games(game_id, game_date, player_a_id, player_a_score, player_b_id, player_b_score)
players(player_id, player_name)

我希望构造一个返回相同结果集，玩家名称和分数的查询，即

game_id，game_date，player_a_name，player_a_score，player_b_name，player_b_score

这是我想要优化的天真方法

select games.game_id, games.game_date, (select player_name from players where player_id = games.player_a_id), games.player_a_score, (select player_name from players where player_id = games.player_b_id), games.player_b_score)

有人能告诉我解决这个问题的最佳方法吗？

谢谢！

Answer 1

也许是这样的：

select
    games.game_id,
    games.game_date,
    pa.player_name as 'player_a_name',
    games.player_a_score,
    pb.player_name as 'player_b_name',
    games.player_b_score
from games
inner join players pa on (games.player_a_id = pa.player_id)
inner join players pb on (games.player_b_id = pb.player_id)

Answer 2

SELECT
  g.game_id, g.game_date, 
  pa.player_name, g.player_a_score, 
  pb.player_name, g.player_b_score
FROM games g
LEFT JOIN player pa ON (pa.player_id=g.player_a_id)
LEFT JOIN player pb ON (pb.player_id=g.player_b_id)

SQL - 一个表的多个连接 - 两个键中的两个值

2 个答案: