MongoDB:如何获取子文档字段值的不同列表?

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假设我收集了以下文档:

Let's say I have the following documents in collection:

{ "family": "Smith", "children": [ { "child_name": "John" }, { "child_name": "Anna" }, ] } { "family": "Williams", "children": [ { "child_name": "Anna" }, { "child_name": "Kevin" }, ] }

现在我想以某种方式获得以下所有家庭的唯一孩子姓名列表:

Now I want to get somehow the following list of unique child names cross all families:

[ "John", "Anna", "Kevin" ]

结果的结构可能不同.如何在 MongoDB 中实现这一点?应该很简单，但我无法弄清楚.我在集合上尝试了 aggregate() 函数，但后来我不知道如何应用 distinct() 函数.

Structure of result might be different. How to achieve that in MongoDB? Should be something simple but I can't figure out. I tried aggregate() function on collection but then I don't know how to apply distinct() function.

推荐答案

你可以这样做:

db.collection.distinct("children.child_name");

在你的情况下它返回:

[ "John", "Anna", "Kevin" ]