再次新的查询。我试图从一小时内解决这个问题。请帮忙

Question

查询：列出所有“朱莉·安德鲁斯”电影的片名和男主角。

一共有三张桌子

电影（id、标题、年份、分数、票数、导演）

演员（身份证，姓名）

铸造（movieid、actorid、ord）

select movie.title,actor.name as cont
from movie
join casting on (movie.id=casting.movieid)
join actor on (casting.actorid=actor.id)
where actor.name='Julie andrews'

其实我不知道怎么找男主角。

Answer 1

您几乎可以肯定需要一个子查询来以一种或另一种方式实现这一目标。

select movie.title, actor.name
from movie
inner join casting 
    on movie.id = casting.movieid
    and casting.ord = 1 --Assuming this is the cast order flag
inner join actor
    on casting.actorid = actor.id
where movie.id in (
    select movie.id
    from movie 
    inner join casting 
        on movie.id = casting.movieid
        and casting.actorid = {your actorID in this case Julie Andrew's id
 )

免责声明：我没有对此进行测试，因为您没有提供简单的方法。

如果您真的想按名称（这可能导致误报），那么您可以在 in 子句子查询中添加一个额外的连接。

Answer 2

首先，你不应该使用id 作为键列，使用movieid 和actorid。这使得连接更容易：

select movie.title, lead.name as cont
  from actor
  join casting             using (actorid)
  join movie               using (movieid)
  join casting as leadrole using (movieid)
  join actor   as lead     on (leadrole.actorid = lead.actorid)
 where actor.name = 'Julie andrews'
   and leadrole.ord = 1

这假定主角的ord 列是 1。它也完全未经测试，因此您可能需要对其进行调试。

Answer 3

假设主角是 ord = 1 你可以试试这个（我没有测试过）

编辑：

select 
      M.title, 
      (select 
            A1.name 
       from 
            casting CI
       join
            actors A1
       on
            A1.id = CI.actorid      
       where 
            CI.movieid = M.id 
       and 
            CI.ord = 1) as LeadingActor 
from 
      movie M
join 
      casting C
on 
      M.id = C.movieid
join 
      actor A 
on 
      C.actorid = A.id
where 
      A.name='Julie andrews'