mysql - 使用自联接的 SQL 查询

Question

我有一张看起来像这样的桌子

YR    Game
1960  football
1961  football
1962  football
1962  tennis
1963  football
1963  golf
1965  football
1965  tennis 
1965  golf
1967  tennis
1967  volleyball

如何使用 join 编写查询以查找必须将足球作为比赛而不是网球的年份..

Answer 1

您可以使用 WHERE 过滤器来获得结果：

select yr, game
from yt
where game = 'Football'
  and yr not in (select yr
                 from yt
                 where game = 'tennis');

请参阅带有演示的 SQL Fiddle

Answer 2

您可以使用连接来过滤它（缺点是您需要两列上的索引）：

SELECT YR FROM table AS a
LEFT JOIN table AS b ON b.YR = a.YR AND b.Game = 'tennis'
WHERE a.Game = 'football' AND b.Game IS NULL

Answer 3

也许这个查询？

select game_year from table_game a left outer join table_game b on a.game_year= 
b.game_year and b.game = 'tennis' where a.game = 'football' and coalesce(b.game, '') = ''