嵌套选择或连接查询？

Question

我对sql很陌生，所以这可能有一个非常基本的答案，但要回答的问题如下……

哪部电影在一场演出中收视率最低？在结果中包括电影名称和电影院名称。？

电影名和电影院名在两个不同的表中，电影和。takings在performance表中。我想不出如何完成这个查询。到目前为止，这是我所得到的，但在第3行第7列中附带了一个错误。

select cinema_no,film_no
from CINEMA, film
where takings ( select min(takings)
from performance);

Answer 1

由于带有oracle的多个标记，我忽略了标记mysql (应该去掉的标记)。请确定您使用的是哪个DBMS，顺便说一下，我已经删除了不相关的oracle-sqldeveloper )。

您似乎需要这样一个select语句(更喜欢使用现代的ANSI-92联接语法，易于维护和理解)，通过降序sum排序和row_number函数的贡献如下：

SELECT Name, Sum_Takings 
  FROM
  (
   SELECT f.Name, sum(p.Takings) Sum_Takings,
          row_number() over (ORDER BY sum(p.Takings)) as rn
     FROM Film f 
     LEFT JOIN Cinema c ON f.Cinema_ID = c.ID
     LEFT JOIN Performance p ON f.ID = p.id_film
    GROUP BY f.Name
   )
  WHERE rn = 1;

添加DDL语句，如下所示：

SQL>  CREATE TABLE Cinema (
  2     ID     integer PRIMARY KEY NOT NULL,
  3     Title  varchar2(100) NOT NULL
  4   );

Table created

SQL>  CREATE TABLE Film (
  2     ID   integer PRIMARY KEY NOT NULL,
  3     Name varchar2(100) NOT NULL,
  4     Cinema_ID integer
  5       CONSTRAINT fk_Cinema_ID REFERENCES Cinema(ID)
  6   );

Table created

SQL>   CREATE TABLE Performance (
  2     ID      integer PRIMARY KEY NOT NULL,
  3     ID_Film integer
  4          CONSTRAINT fk_Film_ID REFERENCES Film(ID),
  5     Takings integer
  6   );

Table created

SQL>  INSERT ALL
  2         INTO Cinema(ID,Title) VALUES(1,'NiteHawk')
  3         INTO Cinema(ID,Title) VALUES(2,'Symphony Space')
  4         INTO Cinema(ID,Title) VALUES(3,'The Ziegfeld')
  5         INTO Cinema(ID,Title) VALUES(4,'Cinema Village')
  6       SELECT * FROM dual;

4 rows inserted

SQL>  INSERT ALL
  2         INTO Film(ID,Name,Cinema_ID) VALUES(1,'Citizen Kane',1)
  3         INTO Film(ID,Name,Cinema_ID) VALUES(2,'Titanic',2)
  4         INTO Film(ID,Name,Cinema_ID) VALUES(3,'Brave Heart',4)
  5         INTO Film(ID,Name,Cinema_ID) VALUES(4,'Dumb and Dummer',3)
  6         INTO Film(ID,Name,Cinema_ID) VALUES(5,'How To Train Your Dragon',2)
  7         INTO Film(ID,Name,Cinema_ID) VALUES(6,'Beetle Juice',3)
  8       SELECT * FROM dual;

6 rows inserted

SQL>  INSERT ALL
  2         INTO Performance VALUES(1,1,15)
  3         INTO Performance VALUES(2,1,4)
  4         INTO Performance VALUES(3,2,10)
  5         INTO Performance VALUES(4,3,1)
  6         INTO Performance VALUES(5,4,5)
  7         INTO Performance VALUES(6,3,3)
  8         INTO Performance VALUES(7,2,7)
  9         INTO Performance VALUES(8,5,7)
 10         INTO Performance VALUES(9,6,6)
 11       SELECT * FROM dual;

9 rows inserted

SQL> commit;

Commit complete

SQL> SELECT Name, Sum_Takings
  2    FROM
  3    (
  4     SELECT f.Name, sum(p.Takings) Sum_Takings,
  5            row_number() over (ORDER BY sum(p.Takings)) as rn
  6       FROM Film f
  7       LEFT JOIN Cinema c ON f.Cinema_ID = c.ID
  8       LEFT JOIN Performance p ON f.ID = p.id_film
  9      GROUP BY f.Name
 10     )
 11    WHERE rn = 1
 12  ;

NAME                                                                  SUM_TAKINGS
--------------------------------------------------------------------- -----------
Brave Heart                                                                     4

https://dbfiddle.uk/?rdbms=oracle_11.2&fiddle=ec76db53517aacecea1c2fa979889fc8

Answer 2

由于涉及性能表的分组，您可以使用两个查询来实现它，一个查询获取最低性能获取的cinemaID和filmID，另一个查询使用收集的ids获取电影院名称和电影名称。

从性能选择CinemaID、FilmID，其中选择PerformanceTaking=(从性能选择最小值(PerformanceTaking))； 从电影中选择CinemaName，FilmName，CinemaID=1和FilmID=1；

Answer 3

这将起作用：

select * from (select c.cinema_name,f.film_name
from cinema c, film f,performance p,
rank() over (partition by c.cinema order by sum(p.takings)) as rank
where
c.ID=f.cinema_id and
f,id=p.id
group by f.film_name) where rank=1
;