如何在MongoDB中按楼层聚合 [英] How to aggregate by floor in MongoDB

问题描述

MongoDB 聚合框架没有 floor 功能.它只有简单的算术运算符.那么，如何使用它们来组合 floor 函数?

MongoDB Aggregation Framework doesn't have floor function. It only has simple arithmetic operators. So, how to compose floor function using them?

推荐答案

根据定义floor(number) = number - (number % step)我们可以组成我们的聚合公式:

According to definition floor(number) = number - (number % step) we can compose our aggregation formula:

{$subtract: ["$number", {$mod: ["$number", <step>]}]}

其中 step 是数量级.首先，它用 $mod 计算余数，然后用 $subtract 计算差.

where step is order of magnitude. First, it computes remainder with $mod and then it computes difference with $subtract.

因此，按age 将用户分组到整个 数字将是

So, grouping Users by age floored to whole numbers will be

db.users.aggregate(
    {$group: {_id: {$subtract: ["$age", {$mod: ["$age", 1]}] }}} )

如果您想下限为 10 或 1000，请使用 10 或 1000 而不是 1.

If you want to floor to 10s or 1000s use 10 or 1000 instead of 1.

这篇关于如何在MongoDB中按楼层聚合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！