Question

这是我关于DVD出租的任务。问题是找到给定类型的前三名著名租借电影。这是我的桌子。

https://drive.google.com/drive/folders/17RuEb-o8tXsAHGYAbjmQmlJaYZZUAEeE?usp=sharing。

下面是我一半完成的怪异代码。

SELECT TOP(3)
FROM MOVIE mv
INNER JOIN DVD dvd ON dvd.movie_id = mv.movie_id
INNER JOIN RENTAL rt ON rt.dvd_id = dvd.dvd_id
WHERE movie_id = movie_id

Answer 1

您有一个好的开始。如果要获得租借最多的电影，则要查询该电影，然后计算租借的次数。然后，选择前3个结果，并按降序排列，并包含WITH TIES提示，以确保您包含与租借次数相同的结果。

SELECT TOP 3 WITH TIES mv.movie, COUNT(rt.id) AS times_rented
FROM MOVIE mv
INNER JOIN DVD dvd ON dvd.movie_id = mv.movie_id
INNER JOIN RENTAL rt ON rt.dvd_id = dvd.dvd_id
GROUP BY mv.movie
ORDER BY COUNT(rt.id) DESC

Answer 2

此查询将返回给定时间段内租借的前N首（有并列）电影的所有电影信息。

declare @StartDate date = '20190601'
    ,@EndDate date = '20190630'
    ,@Top int = 3

;With RentalCounts as
(
SELECT genre, mv.movie_id, Count(*) Ct
FROM MOVIE mv
INNER JOIN DVD dvd ON dvd.movie_id = mv.movie_id
INNER JOIN RENTAL rt ON rt.dvd_id = dvd.dvd_id
WHERE rt.[RentalDate] between @StartDate and @EndDate
group by genre, mv.movie_id
)
, ranked as
(
select *, ranked = rank() over (partition by movie_id, genre order by Ct desc)
from RentalCounts 
)

select mv.*
from ranked r
   join movie m on movie.movie_id = r.MovieID
where ranked.Ct <=@top

我列出了当月特定类型的最受欢迎的三部电影

2 个答案: