如果没有 GROUP BY 子句，将 GROUP 列 (MIN(),MAX(),COUNT(),...) 与没有 GROUP 列的混合是非法的。 Maria DB 中的错误

Question

我正在使用 MariaDB IMDB 电影数据集，我试图解决以下问题。 电影表包含 id、name、rank 和 year 列

A decade is a sequence of 10 consecutive years. For example, say in your database you have movie information starting from 1965. Then the first decade is 1965, 1966, ..., 1974; the second one is 1967, 1968, ..., 1976 and so on. Find the decade D with the largest number of films and the total number of films in D.

当我尝试执行以下查询时出现以下错误SELECT SUM(T3.MOVIE_PER_YEAR), T3.GROUP_PER_DECADE FROM ( SELECT CEIL(T2.ROW_NUM/10) AS GROUP_PER_DECADE, T2.MOVIE_PER_YEAR, T2.YEAR FROM ( SELECT ROW_NUMBER() OVER (ORDER BY T1.YEAR ASC) AS row_num, T1.MOVIE_PER_YEAR, T1.YEAR FROM (SELECT COUNT(M.id) AS MOVIE_PER_YEAR ,M.year FROM movies M GROUP BY M.year )T1 )T2 )T3 GROUP BY GROUP_PER_DECADE;

错误：-

Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause

相同类型的查询在 Oracle DB 中工作。
http://sqlfiddle.com/#!4/cdf8e3/9

请帮我解决这个问题。

Answer 1

不能更简单地完成任务：

SELECT FLOOR(year / 10) * 10 AS decade,
       COUNT(*) AS movies_per_decade
    FROM Movies

例如，假设所有 1980-1989 年都是“1980 年”。

如果您想要“几十年前”，请更改为FLOOR(YEAR(NOW() - year) / 10) AS decades_ago 。

（这适用于任何版本的 MySQL/MariaDB。）