Project operation in Mongo

Project Operation in Mongo.

Example:

[
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a0"), 
    "Emp_Name" : "Jatin", 
    "Emp_Age" : NumberInt(24), 
    "Emp_Salary" : NumberInt(34000), 
    "Emp_Grade" : "B", 
    "Emp_Joining_Date" : ISODate("2020-07-03T18:30:00.000+0000")
}
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a1"), 
    "Emp_Name" : "Terens", 
    "Emp_Age" : NumberInt(27), 
    "Emp_Salary" : NumberInt(34000), 
    "Emp_Grade" : "B", 
    "Emp_Joining_Date" : ISODate("2019-04-03T18:30:00.000+0000")
}
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a2"), 
    "Emp_Name" : "Manu", 
    "Emp_Age" : NumberInt(21), 
    "Emp_Salary" : NumberInt(34000), 
    "Emp_Grade" : "A", 
    "Emp_Joining_Date" : ISODate("2020-07-03T18:30:00.000+0000")
}
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a3"), 
    "Emp_Name" : "Sagun", 
    "Emp_Age" : NumberInt(20), 
    "Emp_Salary" : NumberInt(34000), 
    "Emp_Grade" : "A", 
    "Emp_Joining_Date" : ISODate("2019-01-03T18:30:00.000+0000")
}
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a4"), 
    "Emp_Name" : "Pankaj", 
    "Emp_Age" : NumberInt(60), 
    "Emp_Salary" : NumberInt(34000), 
    "Emp_Grade" : "B", 
    "Emp_Joining_Date" : ISODate("2019-02-03T18:30:00.000+0000")
}
]

Approach

Query: Project operation will make only those fields to view which have project value 1.by default rest of the fields have their value 0 except the primary key.

 
db.getCollection("Employee").aggregate([
    {$match:{"Emp_Grade":"A"}},
    {$project:{"Emp_Name":1,"Emp_Grade":1}}
    ])

Output: 

[
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a3"), 
    "Emp_Name" : "Sagun", 
    "Emp_Grade" : "A", 
}
{ 
    "_id" : ObjectId("60179dd62381fc69d5f1c5a2"), 
    "Emp_Name" : "Manu", 
    "Emp_Grade" : "A", 
}
]