JavaMadeSoEasy.com (JMSE): How to retrieve only specific element from an array in MongoDB

Contents of page >

1) Before retrieve only specific element from an array in MongoDB
2) Let’s use $elemMatch projection operator - It alters the returned document to contain only the first matched element of array.
3) SUMMARY>

How to retrieve only specific element from an array in document in MongoDB

We will use $elemMatch projection operator - It alters the returned document to contain only the first matched element of array.

1) Before retrieve only specific element from an array in MongoDB

Let's create new collection and insert documents in it >

> db.testArr.insert( {CARS : [ { car : "BMW"}, {car : "FERRARI"} ] } )

> db.testCollection.insert({name: 'bcd'})

> db.testCollection.insert({name: 'def'})

First line above will create table (or collection) (if table already exists it will insert documents in it).

Query/Read all documents of collection >

> db.testArr.find();

{ "_id" : ObjectId("585137751317888bda93e53d"), "CARS" : [ { "car" : "BMW" }, { "car" : "FERRARI" } ] }

1 document was found.

2) Let’s use $elemMatch projection operator - It alters the returned document to contain only the first matched element of array.

Now, retrieve only specific element from an array in MongoDB >

> db.testArr.find( {"CARS.car": "BMW"}, {_id: 0, CARS: {$elemMatch: {car: "BMW"}}});

{ "CARS" : [ { "car" : "BMW" } ] }

In our case $elemMatch helped us in retrieving only specific element i.e. BMW and skipped FERRARI.

3) SUMMARY>

So in this mongoDB tutorial we learned how to retrieve only specific element from an array in MongoDB using $elemMatch.

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