Question

我收到以下错误：

Mysql2::Error: Expression #2 of ORDER BY clause is not in GROUP BY clause and contains nonaggregated column 'database_name_development.posts.created_at' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by: SELECT YEAR(created_at) AS year, MONTHNAME(created_at) AS month, COUNT(id) AS total FROM {帖子{1}}

这是我的模型方法

GROUP BY year, month ORDER BY year DESC, MONTH(created_at) DESC

我该如何解决这个问题？

Answer 1

从MySQL 5.6开始，允许SELECT表达式（或相关ORDER BY）中的列的旧默认行为在使用聚合时在GROUP BY中也不会出现更严格（和其他RDBMS一样）。

由于MONTH(created_at)中有ORDER BY以数字方式对月份进行排序，但SELECT和GROUP BY中没有等效表达式，因此违反了MySQL对{{1}的要求}}。解决方案是将数字GROUP BY表达式添加到MONTH()和SELECT，以便分组可以正确聚合。这不应该影响性能。

GROUP BY

如果将def self.archives # Include a MONTH() expression in SELECT Post.unscoped.select("YEAR(created_at) AS year, MONTHNAME(created_at) AS month, MONTH(created_at) AS monthnum, COUNT(id) AS total") # Group with it as well .group("year, month, monthnum") # sort with the column alias .order("year DESC, monthnum DESC") end添加到MONTH(created_at) AS monthnum，可以将.select()保留在.group()之外（因为您实际上不需要返回数值）。如果确实有效，则无法在.group()和.order()中使用别名，而必须使用完整表达式。我不确定这会毫无错误地发挥作用，但相信它可能。

def self.archives
    Post.unscoped.select("YEAR(created_at) AS year, MONTHNAME(created_at) AS month, COUNT(id) AS total")
        # Add the expression to GROUP BY but not SELECT
        .group("year, month, MONTH(created_at)")
        .order("year DESC, MONTH(created_at) DESC")
end

Mysql2 ::错误：ORDER BY子句的表达式＃2不在GROUP BY子句中，并且包含非聚合列

1 个答案: