mongodb query select fields names as code example

Example 1: mongodb select specific fields

db.student.find({}, 'roll _id'); // <--- Just multiple fields name space separated
// OR
db.student.find({}).select('roll _id'); // <--- Just multiple fields name space separated
// OR
db.student.find({}, {'roll' : 1 , '_id' : 1 ); // <---- Old lengthy boring way

Example 2: mongodb select fields

db.inventory.find( { status: "A" }, { item: 1, status: 1 } )

Example 3: mongodb project all fields

db.collection.aggregate([
    { "$addFields": { "custom_field": "$obj.obj_field1" } }
])