CRUD operations and queries

 

CRUD Operations and Queries in MongoDB

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1. Introduction

CRUD stands for:

• Create

• Read

• Update

• Delete

MongoDB performs CRUD operations on documents stored inside collections.

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2. Create Operation (Insert)

Used to add new documents to a collection.

Commands

• insertOne() – insert one document

• insertMany() – insert multiple documents

Example

db.students.insertOne({
  name: "Amit",
  age: 21,
  course: "MCA"
})

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3. Read Operation (Find)

Used to retrieve documents from a collection.

Commands

• find() – fetch all matching documents

• findOne() – fetch a single document

Example

db.students.find({ course: "MCA" })

Query Operators

• $gt – greater than

• $lt – less than

• $eq – equal

db.students.find({ age: { $gt: 20 } })

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4. Update Operation

Used to modify existing documents.

Commands

• updateOne()

• updateMany()

Update Operators

• $set – update a field

• $inc – increment value

Example

db.students.updateOne(
  { name: "Amit" },
  { $set: { age: 22 } }
)

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5. Delete Operation

Used to remove documents from a collection.

Commands

• deleteOne()

• deleteMany()

Example

db.students.deleteOne({ name: "Amit" })

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6. Query Features in MongoDB

MongoDB provides powerful querying features:

Filtering

db.students.find({ age: 21 })

Sorting

db.students.find().sort({ age: 1 })

Limiting Results

db.students.find().limit(5)

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7. Aggregation (Basic Idea)

Used for data analysis and reporting.

Example

db.students.aggregate([
  { $group: { _id: "$course", total: { $sum: 1 } } }
])

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8. Advantages of MongoDB CRUD Operations

• Simple and easy syntax

• JSON-based queries

• High performance

• Flexible data handling