缩短查询

Question

我必须编写一个查询来计算购买的门票数量，该门票仅包含该类型的电影类型。最后，我必须返回电影类型和为该类型购买的门票数量。我写了一个查询，但我想知道它是否可以缩短和更紧凑？

以下是数据库架构：

movies(movieId, movieGenre, moviePrice)
tickets(ticketId, ticketDate, customerId)
details(ticketId, movieId, numOfTickets)

这是我的查询：

select m.genre, count(*)
from(select t.ticketId, m.genre
     from(select d.ticketId
          from(select m.genre, t.ticketId
               from tickets t join details d on t.ticketId = 
                 d.ticketId join movies m on d.movieId = m.movieId
               group by m.genre, t.ticketId) d
          group by d.ticketId
          having count(*) = 1) as t join details d on t.ticketId = 
          d.ticketId join movies m on d.movieId = m.movieId
     group by t.ticketId, m.genre) m
group by m.genre;

这在数据库上运行，所以我只能发布示例输出：

comedy    29821
action    27857
rom-com   19663

Answer 1

我认为没有理由使用表票证，因为结果不会被ticketDate或customerID过滤或聚合。因此，更短的sql是

SELECT m.moviegenre,
       Sum(d.numoftickets) as SumNum
FROM      details d
LEFT JOIN movies m
  ON d.movieid = m.movieid
GROUP  BY m.moviegenre 
HAVING SumNum > 0
ORDER BY m.moviegenre

上午3点28分

我不确定Duplicates是什么意思？在table = details（ticketId，movieId，numOfTickets）?? 我希望ticketId是唯一的，那么什么可以解释重复？ 同一张票是否被打印两次，反复？

确定重复的ticketId数量 -

SELECT ticketId, count(*) as cnt
FROM      details d
GROUP By ticketId
HAVING count(*) > 1

确定重复的“细节”行数 -

SELECT ticketId, movieId, numOfTickets, count(*) as cnt
FROM      details d
GROUP By ticketId, movieId, numOfTickets
HAVING count(*) > 1

然后，它可能是表=电影（movieId，movieGenre，moviePrice）是重复的？确定movieId的重复数量 -

SELECT movieId, count(*) as cnt
FROM   movies m
GROUP BY movieId
HAVING count(*) > 1

从细节中删除重复项 -

SELECT m.moviegenre,
       Sum(d.numoftickets) as SumNum
FROM
   (Select Distinct * From  details) d
LEFT JOIN movies m
  ON d.movieid = m.movieid
GROUP  BY m.moviegenre 
ORDER BY m.moviegenre