Question

我必须编写一个查询，该查询将计算仅包含该类型电影类型的已购买门票的数量。最后，我必须返回电影类型和为此类型购买的门票数量。我已经写了一个查询，但是我想知道它是否可以做得更短，更紧凑？

以下是数据库方案：

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格票证，因为结果不会按ticketDate或customerID进行过滤或汇总。因此，较短的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

添加了3/28 am

我不确定重复是什么意思？在表格中= details（ticketId，movieId，numOfTickets）??
我希望ticketId是唯一的，那么如何解释重复项呢？
同一票证ID是否重复打印两次？

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“详细信息”行数是多少-

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

这又是表=电影（movieId，movieGenre，moviePrice）是重复的那个吗？确定重复的movieId数量-

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

从详细信息中删除重复项-

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

缩短查询

1 个答案: