Question

我有一个包含以下表格的数据库：

ACTOR (id, fname, lname, gender)
MOVIE (id, name, year, rank)
DIRECTOR (id, fname, lname)
CAST (a_id, m_id, role)
MOVIE_DIRECTOR (d_id, m_id)

现在我要检索以下问题的数据。

是：“十年是连续10年的序列。例如，1965、1966，...，1974是十年，1967、1968，...，1976也是如此。电影数量最多的十年”

Answer 1

我可以通过生成年份，加入电影，然后进行汇总来做到这一点：

select y.year as decade_start, y.year + 9 as decade_end,
       count(*) as num_movies
from (select distinct year from movies) y join
     movies m
     on m.year >= y.year and m.year < y.year + 10
group by y.year
order by count(*) desc
limit 1;

Answer 2

您尝试过这样的事情吗？

select
  m.year as decade_begin,
  count(rollup.id) as movies_count
from
  MOVIE m,
  MOVIE rollup
where
  rollup.year >= decade_begin and rollup.year < decade_begin+10
group by
  decade_begin
order by
  movies_count;

Answer 3

在这里，只有MOVIE表才很重要。

在MySql 8.x中，可以为此使用CTE上的自联接。

WITH MOV AS
(
   SELECT year as movie_year, COUNT(id) as total_movies
   FROM MOVIE 
   GROUP BY year
)
SELECT
  m1.movie_year as decade_start,
  MAX(m2.movie_year) as decade_end,
  SUM(m2.total_movies) as total_movies
FROM MOV m1
LEFT JOIN MOV m2 ON (m2.movie_year BETWEEN m1.movie_year AND m1.movie_year + 9)
GROUP BY m1.movie_year
ORDER BY SUM(m2.total_movies) DESC
LIMIT 1

在不支持CTE的MySql 5.x中，只需用来自CTE的查询的子查询替换m1和m2的MOV。

SQL查询查找记录数量最多的十年

3 个答案: