Syntax error Projection result as an array of selected items in MongoDB?

Projection result as an array of selected items in MongoDB?

Use the distinct() for this, since it finds the distinct values for a specified field across a single collection or view and returns the results in an array.

Let us first create a collection with documents −

> db.projectionListDemo.insertOne({"_id":"1","Subject":["MongoDB","MySQL","Java"]});
{ "acknowledged" : true, "insertedId" : "1" }
> db.projectionListDemo.insertOne({"_id":"2","Subject":["MongoDB","C","C++"]});
{ "acknowledged" : true, "insertedId" : "2" }
> db.projectionListDemo.insertOne({"_id":"3","Subject":["Java","Python"]});
{ "acknowledged" : true, "insertedId" : "3" }

Display all documents from a collection with the help of find() method −

> db.projectionListDemo.find().pretty();

Output

{ "_id" : "1", "Subject" : [ "MongoDB", "MySQL", "Java" ] }
{ "_id" : "2", "Subject" : [ "MongoDB", "C", "C++" ] }
{ "_id" : "3", "Subject" : [ "Java", "Python" ] }

Now, let us get result as an array of selected items −

> db.projectionListDemo.distinct('_id', {'Subject' : 'MongoDB'});

Output

[ "1", "2" ]
Updated on: 2019-07-30T22:30:26+05:30

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