Question

使用以下数据库架构，找到仅提供Joe喜欢的啤酒的酒吧

Beers(name, manf)
Bars(name, addr, license)
Drinkers(name, addr, phone)
Likes(drinker, beer)
Sells(bar, beer, price)
Frequents(drinker, bar)

这是我的尝试：

SELECT b.name
FROM bars b
WHERE NOT EXISTS
    (SELECT l.beer
    FROM likes l
    WHERE l.drinker = 'joe' AND NOT EXISTS
        (SELECT *
        FROM sells s 
        WHERE l.beer = s.beer AND b.name = s.bar))

我的尝试返回了供应啤酒乔喜欢的酒吧，而不是仅供应他喜欢的啤酒的酒吧。关于我出错的地方的任何帮助都会有所帮助

Answer 1

可能是这些酒吧

select bar 
from Sells not in (
        select  bar 
        from Sells 
        where beer  not in (select beer from likes where drinker = 'joe')
)

MySQL非单调查询

1 个答案: