如何在 MongoDB 中查询字典数组? [英] How do I query an array of dictionaries in MongoDB?

问题描述

我有一组字典，我必须在这些字典上进行查询.查询将类似于当名称"为a"时，值"应为2".

I have an array of dictionaries on which I have to make queries. The queries will be like when "name" is "a" then "value" should be "2".

{
    "t": "m",
    "y": "n",
    "A":[ 
            {
             "name": "x",
             "value": "1"
            },
            {
             "name": "y",
             "value": "2"
            },
            {
             "name": "z",
             "value": "1"
            }
        ]
}

在上面，我想知道当name"为x时，value"为1"的记录是什么.我还需要进行查询，其中名称"为x"，则值应为2"，名称"为y"，则值"应为1"

In the above, I want to know what are the records whose "value" is "1" when "name" is x. I also need to make queries like, where "name" is "x" then value should be "2" and "name" is "y" then "value" should be "1"

推荐答案

你必须使用 $elemMatch 查询数组中的嵌入文档，如果你想查询嵌入文档的多个字段.所以你的查询应该是这样的:

You have to use $elemMatch to query embedded documents in an array if you want to query with multiple fields of embedded document. So your query should be like this:

db.collection.find( {
  "A": { $elemMatch: { name: "x", value: "1" } }
})

如果您想查询具有 (name:"x", value:"1") 或 (name:"y", value:"2") 在同一个查询中，你可以像这样使用 $or 和 elemMatch:

If you want query documents which have (name:"x", value:"1") or (name:"y", value:"2") in same query, you can use $orwith elemMatch like this:

db.collection.find( {
  $or: [
    { "A": { $elemMatch: { name: "x", value: "1" } } },
    { "A": { $elemMatch: { name: "y", value: "2" } } }
  ]  
})

如果您想要查询具有 (name:"x", value:"1") 和 (name:"y", value:"2") 在同一个查询中，你可以像这样使用 $and 和 elemMatch:

If you want query documents which have (name:"x", value:"1") and (name:"y", value:"2") in same query, you can use $andwith elemMatch like this:

db.collection.find( {
  $and: [
    { "A": { $elemMatch: { name: "x", value: "1" } } },
    { "A": { $elemMatch: { name: "y", value: "2" } } }
  ]  
})

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