MongoDB获取1字段的所有值 [英] MongoDB get all values of 1 field

问题描述

所以我知道在mongodb中，我可以获取所有值，然后遍历它们，但是我想知道在mongodb中是否可以选择仅获取某个字段.

So I know that in mongodb, I can get all values and then iterate through them but I was wondering if in mongodb there is an option to get only a certain field.

例如，假设我的收藏的结构如下:

So for example suppose my collection is structured as follows:

{_id:
    {
    field1,field2,field3}
    }
{description:
    {
    field1,field2,field3,
    data:{
    field1,field2,field3
    }
    }
    }
{otherdata:
{field1,field2,field3}
}

现在，我需要description.data.field1的值，那么有关如何执行此操作的任何建议?

Now, I need the value of description.data.field1 so any suggestions on how to do that?

到目前为止，我已经尝试使用以下命令:

So far I have tried using following commands:

db.module.collection.description.data.find()
db.module.collection.description.find({'data':1})
db.module.collection.find('description.data.data':1})

但是显然，它们没有用.

But obviously, they did not work.

有什么建议吗?

推荐答案

首先，JSON的结构不正确.正确的结构应为:

First of all, the structure of your JSON isn't correct. The correct structure should be:

{
_id:{
    field1: "",
    field2: "",
    field3: ""
},
description:{
    field1: "",
    field2: "",
    field3: "",
    data:{
        field1: "",
        field2: "",
        field3: ""
    }
},
otherdata:{
    field1: "",
    field2: "",
    field3: ""
}
}

现在，您可以使用 Projections

类似这样的东西:

db.collection.find({}, {description.data.field1: 1})

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