CRUD Operations¶

Introduction¶

CRUD stands for Create, Read, Update, Delete - the four basic operations you can perform on a database. MongoDB is a NoSQL database that stores data in JSON-like documents (BSON).

1. Create (Insert)¶

Insert One Document¶

db.collectionName.insertOne({
    name: "Rahul",
    age: 16,
    city: "Delhi"
});

Insert Many Documents¶

db.collectionName.insertMany([
    { name: "Ravi", age: 17, city: "Mumbai" },
    { name: "Sara", age: 15, city: "Bangalore" }
]);

2. Read (Query)¶

Find All Documents¶

db.collectionName.find();

Find One Document¶

db.collectionName.findOne({ name: "Lily" });

Find with Conditions¶

db.collectionName.find({ age: { $gt: 15 } }); // age greater than 15

Projection (Select Fields)¶

db.collectionName.find({ age: { $gt: 15 } }, { name: 1, city: 1, _id: 0 });

3. Update¶

Update One Document¶

db.collectionName.updateOne(
    { name: "Piyush" },
    { $set: { city: "Noida" } }
);

Update Many Documents¶

db.collectionName.updateMany(
    { age: { $lt: 17 } },
    { $set: { status: "minor" } }
);

Replace a Document¶

db.collectionName.replaceOne(
    { name: "Sara" },
    { name: "Sara", age: 16, city: "Pune" }
);

4. Delete¶

Delete One Document¶

db.collectionName.deleteOne({ name: "Ravi" });

Delete Many Documents¶

db.collectionName.deleteMany({ age: { $lt: 16 } });

5. Common Operators¶

$gt → Greater than
$lt → Less than
$gte → Greater than or equal
$lte → Less than or equal
$ne → Not equal
$in → Matches any value in an array
$nin → Matches none in an array
$set → Updates specified fields
$unset → Removes specified fields

Example Flow¶

// 1. Create
db.students.insertOne({ name: "Chris", age: 16, grade: "10th" });

// 2. Read
db.students.find({ age: { $gte: 16 } });

// 3. Update
db.students.updateOne({ name: "Chris" }, { $set: { grade: "11th" } });

// 4. Delete
db.students.deleteOne({ name: "Chris" });