MongoDb查询条件比较2个字段 [英] MongoDb query condition on comparing 2 fields

问题描述

我有一个集合T，有2个字段：Grade1和Grade2，我想选择条件Grade1> Grade2，如何获得像MySQL中的查询？
选择* from T Where 1> Grade 2

I have a collection T, with 2 fields: Grade1 and Grade2, and I want to select those with condition "Grade1 > Grade2", how can I get a query like in MySQL? Select * from T Where Grade1 > Grade2

推荐答案

只要知道它会相当慢（必须在每个记录上执行Javascript代码），因此结合索引查询，如果可以。

You can use a $where. Just be aware it will be fairly slow (has to execute Javascript code on every record) so combine with indexed queries if you can.

db.T.find( { $where: function() { return this.Grade1 > this.Grade2 } } );

或更紧凑：

db.T.find( { $where : "this.Grade1 > this.Grade2" } );

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