MongoDB 高级查询

发布于 2024-10-22 01:15:56 字数 450 浏览 1 评论 0原文

假设我有一个具有两个属性的集合：amount 和 amountreceived 都是小数。

我想编写一个查询，该查询将从集合中返回满足金额大于收到金额条件的项目。

目前我有一个如下所示的 javascript 函数：

f = function() { return this.amount > this.amountreceived;}

我还有一个如下所示的集合集：

item1 : amount = 50, amountreceived = 0;
item2 : amount = 50, amountreceived = 25;

如果我运行 db.MyCollection.find(f) ，则返回的唯一结果是 item1。

关于为什么该查询不会返回两个结果有什么想法吗？

原文

Let's say I have a Collection with two properties: amount and amountreceived that are decimals.

I want to write a query that will return items from the collection that meet the criteria of the amount being greater than the amount received.

Currently I have a javascript function that looks like this:

f = function() { return this.amount > this.amountreceived;}

I also have a collection set that looks like this:

item1 : amount = 50, amountreceived = 0;
item2 : amount = 50, amountreceived = 25;

If I run db.MyCollection.find(f) the only result returned is item1.

Any ideas on why that query will not return both results?

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焚却相思 2024-10-29 01:15:56

我假设您使用的是 C# 驱动程序？由于 BSON 没有十进制数据类型，C# 驱动程序必须以某种方式表示 .NET 十进制值。默认表示形式是字符串，这有利于不丢失任何精度，但不利于执行查询。

您还可以要求 C# 驱动程序将 .NET 十进制值存储为 BSON 双精度数，这会导致一些精度损失并可能溢出，但有利于查询。

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Oo萌小芽oO 2024-10-29 01:15:56

您确定您这样做正确吗？对于我下面的例子，你有一个反例吗？

这是我的示例测试脚本，它可以工作。（db.foo 为空）

MongoDB shell version: 1.6.5
connecting to: test
> db.foo.insert( {_id : 1, amount : 50, amtreceived : 100 } )
> db.foo.insert( {_id : 2, amount : 50, amtreceived : 25 } )
> db.foo.insert( {_id : 3, amount : 50, amtreceived : 0 } )
> db.foo.find()
{ "_id" : 1, "amount" : 50, "amtreceived" : 100 }
{ "_id" : 2, "amount" : 50, "amtreceived" : 25 }
{ "_id" : 3, "amount" : 50, "amtreceived" : 0 }
> f = function() { return this.amount > this.amtreceived; }
function () {
    return this.amount > this.amtreceived;
}
> db.foo.find(f) // expect 2 & 3
{ "_id" : 2, "amount" : 50, "amtreceived" : 25 }
{ "_id" : 3, "amount" : 50, "amtreceived" : 0 }

Are you sure that you are doing this correctly? Do you have a counter-example for my example below?

Here's my sample test script where this works. (db.foo is empty)

MongoDB shell version: 1.6.5
connecting to: test
> db.foo.insert( {_id : 1, amount : 50, amtreceived : 100 } )
> db.foo.insert( {_id : 2, amount : 50, amtreceived : 25 } )
> db.foo.insert( {_id : 3, amount : 50, amtreceived : 0 } )
> db.foo.find()
{ "_id" : 1, "amount" : 50, "amtreceived" : 100 }
{ "_id" : 2, "amount" : 50, "amtreceived" : 25 }
{ "_id" : 3, "amount" : 50, "amtreceived" : 0 }
> f = function() { return this.amount > this.amtreceived; }
function () {
    return this.amount > this.amtreceived;
}
> db.foo.find(f) // expect 2 & 3
{ "_id" : 2, "amount" : 50, "amtreceived" : 25 }
{ "_id" : 3, "amount" : 50, "amtreceived" : 0 }

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