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How to query documents by a condition on the subdocument in MongoDB?
Let us first create a collection with documents −
> db.demo394.insertOne( ... { ... ... details: [ ... { ... _id: '1', ... startDate: '2018-01-11T07:00:00.000Z', ... endDate: '2019-01-12T07:59:59.999Z' ... }, ... { ... _id: '2', ... startDate: '2019-01-21T07:00:00.000Z', ... endDate: '2020-01-04T07:59:59.999Z' ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e5e716817aa3ef9ab8ab202") }
Display all documents from a collection with the help of find() method −
> db.demo394.find();
This will produce the following output −
{ "_id" : ObjectId("5e5e716817aa3ef9ab8ab202"), "details" : [ { "_id" : "1", "startDate" : "2018-01-11T07:00:00.000Z", "endDate" : "2019-01-12T07:59:59.999Z" }, { "_id" : "2", "startDate" : "2019-01-21T07:00:00.000Z", "endDate" : "2020-01-04T07:59:59.999Z" } ] }
Following is how to query documents by a condition on the subdocument −
> db.demo394.find({ ... $expr: { ... $let: { ... vars: { "d": { $arrayElemAt: [ "$details", -1 ] } }, ... in: { $eq: [ "$$d.endDate", "2020-01-04T07:59:59.999Z" ] } ... } ... } ... })
This will produce the following output −
{ "_id" : ObjectId("5e5e716817aa3ef9ab8ab202"), "details" : [ { "_id" : "1", "startDate" : "2018-01-11T07:00:00.000Z", "endDate" : "2019-01-12T07:59:59.999Z" }, { "_id" : "2", "startDate" : "2019-01-21T07:00:00.000Z", "endDate" : "2020-01-04T07:59:59.999Z" } ] }
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