How can I get multiple elements from an array in MongoDB?

Question

How can I get multiple elements from an array at once that satisfy a specific condition, for example: Date <= 2020-12-31. I read about $elemMatch, but I can only get one specific element with it.

"someArray": [
            {
                "Date": "2021-09-30",
                "value": "6.62"
            },
            {
                "Date": "2020-12-31",
                "value": "8.67"
            },
            {
                "Date": "2019-12-31",
                "value": "12.81"
            },
            {
                "Date": "2018-12-31",
                "value": "13.82"
            },
            {
                "Date": "2017-12-31",
                "value": "13.83"
            },
            ...
            ]

J.F. · Accepted Answer · 2021-11-13 19:11:59Z

1

You can use $filter in an aggregation query like this:

db.collection.aggregate([
  {
    "$project": {
      "someArray": {
        "$filter": {
          "input": "$someArray",
          "as": "a",
          "cond": {
            "$lte": [
              "$$a.Date",
              ISODate("2020-12-31")
            ]
          }
        }
      }
    }
  }
])

Example here

Note that you can use $project or $set (available since version 4.2): example or $addFields: example

answered Nov 13, 2021 at 19:11

J.F.

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2 Comments

sorohimm Over a year ago

Thank you, it helped me! And how can I add another condition, for example, Data >= 2017-12-31?

J.F. Over a year ago

Use $and to add multiple conditions into cond. Check this example

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