PostgreSQL 条件连接和结果过滤

如何解决PostgreSQL 条件连接和结果过滤

我想要什么

出演过多个相同角色的演员的名字 导演的电影（但不是他们自己导演的）并且自己导演了至少一部电影。

select * from moviesdirectors LIMIT 5

前 5 名电影导演行

movieid   director
6       Bob Persichetti
6       Peter Ramsey
6       Rodney Rothman
16      Sergio Leone
20      Spike Jonze

和

select * from moviescast LIMIT 5

电影播放前 5 行

movieid castname
427     Quei Tann
2878    Indrans
3272    Togo Igawa
517     Ajay Naidu
1608    Megan Sousa

我的尝试：

select * from moviescast LEFT JOIN moviesdirectors ON moviesdirectors.movieid=moviescast.movieid
where castname in (select director from moviesdirectors) AND castname!=director 
ORDER BY castname

解决方法

如果我正确理解了你的问题，你想算上演员：

1. 执导一部或多部电影
2. 为同一位导演出演了不止一部电影，但该电影不应该让他们担任联合导演。

如果是这样的话，我用

复制了一个与你相似的数据集

create table moviesdirectors( movieid int,director varchar);
 create table moviescast( movieid int,castname varchar);
 
 insert into moviesdirectors values(6,'Bob Persichetti');
 insert into moviesdirectors values(6,'Peter Ramsey');
 insert into moviesdirectors values(6,'Rodney Rothman');
 insert into moviesdirectors values(10,'Sergio Leone');
 insert into moviesdirectors values(10,'Spike Jonze');
 insert into moviesdirectors values(20,'Spike Jonze');

 insert into moviescast values(6,'Bob Persichetti');
 insert into moviescast values(20,'Bob Persichetti');
 insert into moviescast values(10,'Bob Persichetti');
 insert into moviescast values(6,'Quei Tann');
 insert into moviescast values(20,'Quei Tann');
 insert into moviescast values(10,'Quei Tann');
 insert into moviescast values(6,'Sergio Leone');
 insert into moviescast values(20,'Sergio Leone');
 insert into moviescast values(6,'Peter Ramsey');
 insert into moviescast values(20,'Peter Ramsey');

表 moviesdirectors 现在包含以下内容

 movieid |    director     
---------+-----------------
       6 | Bob Persichetti
       6 | Peter Ramsey
       6 | Rodney Rothman
      10 | Sergio Leone
      10 | Spike Jonze
      20 | Spike Jonze
(6 rows)

和表 moviescast 以下

 movieid |    castname     
---------+-----------------
       6 | Bob Persichetti
      20 | Bob Persichetti
      10 | Bob Persichetti
       6 | Quei Tann
      20 | Quei Tann
      10 | Quei Tann
       6 | Sergio Leone
      20 | Sergio Leone
       6 | Peter Ramsey
      20 | Peter Ramsey
(10 rows)

在上述数据集中，只有为 Bob Persichetti 工作的 Spike Jonze 应满足最初陈述的 2 个条件。

其余的都不应该，因为：

• Quei Tann 从未导演过
• Sergio Leone 曾出演两部电影，但导演不同
• Peter Ramsey 出演了两部电影，但只有一部（movieid=6 也是他自己导演的）

为了提供解决方案，我将问题分为以下查询的各个步骤：

1. directed_by_themselves：检索 movieid 的列表，其中 director 也是演员表的一部分
2. directors：检索不同的董事列表
3. 最后一个查询将所有内容粘合在一起，并从结果数据集中删除所有演员同时也是导演的电影

with directed_by_themselves as (
  select distinct moviesdirectors.movieid,moviesdirectors.director 
  from moviesdirectors join moviescast 
  on moviesdirectors.movieid = moviescast.movieid 
  and moviesdirectors.director = moviescast.castname
 ),directors as (
 select distinct director from moviesdirectors) 
 
 select d.director,c.castname,count(*) nr_movies 
 from moviesdirectors d join moviescast c
 on (d.movieid = c.movieid)
 join directors dir on c.castname = dir.director
 where (d.movieid,c.castname) not in (select movieid,director from directed_by_themselves)
 group by d.director,c.castname
 having count(*) > 1;

结果是

  director   |    castname     | nr_movies 
-------------+-----------------+-----------
 Spike Jonze | Bob Persichetti |         2
(1 row)