我需要创建一个SQL视图，将每个电影的以下信息相关联：
1）电影的放映次数
2）每次电影放映中的预告片数量及其长度
3）每次电影放映中出现的斑点数量及其长度
我为请求的时间长而对不起，但我试图做到更加清晰。
我有这些表：
FILM-> id_film主键
id_film film_title
1 'Iron Man'
2 'Spider Man'
3 'Thor'
Screening_film-> id_screening主键，id_film外键引用电影（id_film）
id_screening id_film
1 1
2 2
3 3
4 3
SPOT-> id_spot主键
id_spot lenght
1 10
2 20
3 30
TRAILER-> id_trailer主键
id_trailer lenght
4 10
5 20
6 30
Spot_trailer_screening->此表中有现货/预告片和电影之间的关联
id_ST id_film
1 1
2 2
3 3
4 1
5 2
6 3
这是我的代码：
CREATE VIEW film_list AS
SELECT f.film_title,
count(x.id_screening) number_of_screening, count (s.id_spot) num_spot,
sum(s.lenght) spot_lenght, count(t.id_trailer) num_trailer,
sum(t.lenght) trailer_lenght
FROM film f
FULL OUTER JOIN screening_film x
ON x.id_film = f.id_film
FULL OUTER JOIN spot_trailer_screening y --The problems begin with this join, the count of number_of_screening isn't correct--
ON y.id_film = f.id_film
FULL OUTER JOIN spot s
ON s.id_spot = y.id_st
FULL OUTER JOIN trailer t
ON t.id_trailer = y.id_st
GROUP BY f.id_film, f.film_title;
输出：
FILM_TITLE NUMBER_OF_SCREENING NUM_SPOT SPOT_LENGHT NUM_TRAILER TRAILER_LENGHT
Iron Man 2 1 10 1 10
Spider Man 2 1 20 1 20
Thor 4 2 60 2 60
正确的输出应该是以下内容：
FILM_TITLE NUMBER_OF_SCREENING NUM_SPOT SPOT_LENGHT NUM_TRAILER TRAILER_LENGHT
Iron Man 1 1 10 1 10
Spider Man 1 1 20 1 20
Thor 2 1 30 1 30
大量示例数据（第1至32行）使查询时间很长。当然，您拥有这些表，因此您的“实际”查询从第33行开始。
接下来的3个CTE（第34-53行）（t_screening，t_spot和t_trailer）用于计算所需的一切，并避免在查询中获得duplicate值。
最后，最后一个查询（从第55行开始）仅连接已计算的内容。如果有些电影没有预告片或斑点，则必须使用外部连接。但是，由于示例数据表明有所不同，因此我使用了内部联接。
正如我所说：相当长的查询，所以我将其分为3部分以提高可读性：
样本数据：
SQL> with
2 -- sample data
3 film (id_film, film_title) as
4 -- I wish I were 12 again ... I'd LOVE these films
5 (select 1, 'Iron Man' from dual union all
6 select 2, 'Spider Man' from dual union all
7 select 3, 'Thor' from dual
8 ),
9 screening_film (id_screening, id_film) as
10 (select 1, 1 from dual union all
11 select 2, 2 from dual union all
12 select 3, 3 from dual union all
13 select 4, 3 from dual
14 ),
15 spot (id_spot, length) as
16 (select 1, 10 from dual union all
17 select 2, 20 from dual union all
18 select 3, 30 from dual
19 ),
20 trailer (id_trailer, length) as
21 (select 4, 10 from dual union all
22 select 5, 20 from dual union all
23 select 6, 30 from dual
24 ),
25 spot_trailer_screening (id_st, id_film) as
26 (select 1, 1 from dual union all
27 select 2, 2 from dual union all
28 select 3, 3 from dual union all
29 select 4, 1 from dual union all
30 select 5, 2 from dual union all
31 select 6, 3 from dual
32 ),
计算：
33 -- calculation
34 t_screening as
35 (select s.id_film,
36 count(*) cnt_screening
37 from screening_film s join film f on f.id_film = s.id_film
38 group by s.id_film
39 ),
40 t_spot as
41 (select sts.id_film,
42 count(*) cnt_spot,
43 sum(s.length) len_spot
44 from spot_trailer_screening sts join spot s on sts.id_st = s.id_spot
45 group by sts.id_film
46 ),
47 t_trailer as
48 (select sts.id_film,
49 count(*) cnt_trailer,
50 sum(t.length) len_trailer
51 from spot_trailer_screening sts join trailer t on sts.id_st = t.id_trailer
52 group by sts.id_film
53 )
最终查询：
54 -- final query
55 select f.id_film,
56 f.film_title,
57 c.cnt_screening,
58 --
59 s.cnt_spot,
60 s.len_spot,
61 --
62 t.cnt_trailer,
63 t.len_trailer
64 from film f join t_screening c on c.id_film = f.id_film
65 join t_spot s on s.id_film = f.id_film
66 join t_trailer t on t.id_film = f.id_film
67 order by f.id_film;
ID_FILM FILM_TITLE CNT_SCREENING CNT_SPOT LEN_SPOT CNT_TRAILER LEN_TRAILER
---------- ---------- ------------- ---------- ---------- ----------- -----------
1 Iron Man 1 1 10 1 10
2 Spider Man 1 1 20 1 20
3 Thor 2 1 30 1 30
SQL>
您的餐桌有问题。您必须标准化表Spot_trailer_screening。因为当您通过Film将该表与表id_film联接时，您的记录是重复的。您必须将表Spot_trailer_screening分为两个表Spot_screening(id_spot, id_film)和Trailer_screening(id_trailer, id_film)。您将使用这两个表进行联接。