查找列的最大值，按不同 table 中的列分组

Question

我正在尝试为上述 database/tables 编写一个查询，该查询将 return 每个导演排名最高的电影。

我试过：

SELECT d.id, md.movie_id, m.name, m.year, MAX(m.rank)
FROM directors d
INNER JOIN movies_directors md
ON d.id = md.director_id
INNER JOIN movies m
ON md.movie_id = m.id
GROUP BY d.id

但它是 returning:

[Code: 8120, SQL State: S0001]  Column 'movies_directors.movie_id' is invalid in the select list 
because it is not contained in either an aggregate function or the GROUP BY clause.

Answer 1

这是每组前一题。您需要某种过滤逻辑而不是聚合。

您通常可以为此使用 row_number()：

select *
from (
    select 
        d.id, 
        md.movie_id, 
        m.name, 
        m.year, 
        row_number() over(partition by d.id order by m.rank desc) rn
    from directors d
    inner join movies_directors md on d.id = md.director_id
    inner join movies m on md.movie_id = m.id
) t
where rn = 1

查找列的最大值，按不同 table 中的列分组

Finding the max value for a column, grouped by a column in a different table

sql

tsql

sql-server

join

greatest-n-per-group