JavaMadeSoEasy.com (JMSE): $type aggregation operator in MongoDB - To display type of the field in document

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$type aggregation operator

$type aggregation operator returns the type of the field in document.

1) First let's create insert documents in collection in MongoDB

1.1) Let's create new collection and insert document in it before finding >

We will insert values of different type in document.

db.testColl.insert( { _id: 1, name : "ankit" }) //string

db.testColl.insert({ _id: 2, name : 11 }) //double

db.testColl.insert( { _id: 3, name : NumberLong(12) }) //long

db.testColl.insert({ _id: 4, name : [ 21, 21.2 ] }) //array

db.testColl.insert( { _id: 5, name : {city: "delhi"} } ) //object

db.testColl.insert({ _id: 6 }) //missing

Above will create collection (or table) (if collection already exists it will insert documents in it).

1.2) Let’s query all documents of collection using find() method>

> db.testColl.find()

Output>

{ "_id" : 1, "name" : "ankit" }

{ "_id" : 2, "name" : 11 }

{ "_id" : 3, "name" : NumberLong(12) }

{ "_id" : 4, "name" : [ 21, 21.2 ] }

{ "_id" : 5, "name" : { "city" : "delhi" } }

{ "_id" : 6 }

2) Now, Write query which display type of field “name” >

We will use $type operator.

db.testColl.aggregate([{
   $project: {
      typeOf_name : { $type: "$name" }
   }
}])

Note : $type can be used in MongoDB 3.4 or above.

Summary -

So in this MongoDB tutorial we learned about $type aggregation operator in MongoDB - To display type of the field in document

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Labels: MongoDB MongoDB operators