使用不包含特定值的数组查找文档 [英] Find documents with array that doesn't contains a specific value

问题描述

我有以下模型:

var PersonSchema = new Schema({
    name: String,
    groups: [
        {type: Schema.Types.ObjectId, ref: 'Group'}
    ],
});

我正在寻找一个查询来检索不属于某个组的所有人员(即人员的组数组不包含指定组的 id).

I am looking for a query that retrieves all the Persons that are not part of a certain Group (i.e the persons' group array doesn't contain the id of the specified group).

我正在考虑这样的事情，但我不确定它是否正确:

I was thinking about something like this, but I'm not sure it is correct:

Person.find({groups: {$nin: [group._id]})

推荐答案

您基本上尝试的内容没有错，但也许这里唯一的澄清是常见的误解，即您需要像 $nin 或 $in 查询数组时.

Nothing wrong with what you are basically attempting, but perhaps the only clarification here is the common misconception that you need operators like $nin or $in when querying an array.

此外你真的需要在这里做一个基本的不等式匹配$ne:

Also you really need to do here is a basic inequality match with $ne:

Person.find({ "groups": { "$ne": group._id } })

数组"运算符不是用于数组目标"，而是用于以方便的形式提供要测试的条件列表".

The "array" operators are not for "array targets" but for providing a "list" of conditions to test in a convenient form.

Person.find({ "groups": { "$nin": [oneId, twoId,threeId] } })

因此只需对单个条件使用普通运算符，并保存 $in 和 $nin 以用于您想要针对单个值或一个值测试多个条件的地方列表.所以情况正好相反.

So just use normal operators for single conditions, and save $in and $nin for where you want to test more than one condition against either a single value or a list. So it's just the other way around.

如果您确实需要传递参数的列表"，其中提供的列表中的无"与数组的内容匹配，那么您可以使用 $not 运算符和 $all 运算符:

If you do need to pass a "list" of arguments where "none" of those in the provided list match the contents of the array then you reverse the logic with the $not operator and the $all operator:

Person.find({ "groups": { "$not": { "$all": [oneId,twoId,threeId] } } })

所以这意味着数组中不存在提供的列表中的任何一个".

So that means that "none of the list" provided are present in the array.

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