CRUD is an abbreviation for four basic database operations:

Example: In a student management system, CRUD operations help you register students, view their details, update their courses, and delete records when necessary.

Open MongoDB Shell (mongosh) and select a database named school.

use school

Create a collection named students if it does not already exist.

db.createCollection("students")

If the collection already exists, MongoDB will report that it already exists. You can continue using it.

The Create operation adds new documents to a collection. MongoDB provides methods such as insertOne() and insertMany().

Example 1: Insert One Student

db.students.insertOne({
    name: "Rahul",
    age: 20,
    course: "ADCA",
    city: "Aurangabad"
})

This command inserts one student document into the students collection.

Example 2: Insert Multiple Students

db.students.insertMany([
    {
        name: "Amit",
        age: 21,
        course: "Tally Prime",
        city: "Patna"
    },
    {
        name: "Priya",
        age: 19,
        course: "Web Development",
        city: "Gaya"
    },
    {
        name: "Neha",
        age: 22,
        course: "Python",
        city: "Aurangabad"
    }
])

Result: New student documents are added to the collection.

The Read operation retrieves documents from a collection. MongoDB provides the find() and findOne() methods.

Example 1: Display All Students

db.students.find()

Example 2: Display One Student

db.students.findOne({
    name: "Rahul"
})

Example 3: Find Students by Course

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

Example 4: Find Students by City

db.students.find({
    city: "Aurangabad"
})

Result: MongoDB displays documents that match the specified query.

The Update operation modifies existing documents. The updateOne() method updates the first matching document.

Example 1: Update a Student's Age

db.students.updateOne(
    { name: "Rahul" },
    { $set: { age: 21 } }
)

The age of the first student named Rahul is changed to 21.

Example 2: Update a Student's Course

db.students.updateOne(
    { name: "Amit" },
    { $set: { course: "Python" } }
)

Example 3: Update Multiple Documents

db.students.updateMany(
    { city: "Aurangabad" },
    { $set: { status: "Active" } }
)

Use updateMany() when you want to modify every document matching the filter.

Result: The specified field values are updated in the matching documents.

The Delete operation removes documents from a collection. MongoDB provides deleteOne() and deleteMany().

Example 1: Delete One Student

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

This removes the first document matching the name Rahul.

Example 2: Delete Multiple Students

db.students.deleteMany({
    status: "Inactive"
})

This removes all documents whose status is Inactive.

The following example demonstrates all four CRUD operations using one student document.

Step 1: Create

db.students.insertOne({
    name: "Suman",
    age: 20,
    course: "JavaScript"
})

Step 2: Read

db.students.find({
    name: "Suman"
})

Step 3: Update

db.students.updateOne(
    { name: "Suman" },
    { $set: { age: 21 } }
)

Step 4: Read the Updated Document

db.students.findOne({
    name: "Suman"
})

Step 5: Delete

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

Step 6: Verify Deletion

db.students.find({
    name: "Suman"
})

If no matching document remains, the final query returns no document.

Create a database named college and a collection named students. Complete these tasks using MongoDB Shell:

1. Insert five student documents.
2. Include name, age, course, and city fields.
3. Display all student records.
4. Find students enrolled in Python.
5. Find one student by name.
6. Update one student's age.
7. Change a student's course.
8. Delete one student by name.
9. Display all remaining student documents.

Challenge: Use updateMany() to add a field named status with the value "Active" to all students in your practice collection.