Lectures.txt

MongoDB:
    1. A document oriented non-relational NoSQL Database.
    2. Store data in a document 
        - Each document has field (key-value apirs)
        - Each document is a json object
    3. Flexibility
        - Schema less
    4. Performance
        -> Indexing
        -> Embeded documents
        -> Sherding
        {   
            "_id": 1,
            'name": "Zakir",
            "email": "zakir@gmail.com",
            "courses": ["WAF", "CC", "CG"].
            courseInfo: [{"_id": 1, "title": "Web A..", ...},{"":"", "":"", ...}]-> emebedding documents, Nexted document objects.

        }
    5. Free and Open source

    - Internally it is in BSON Format.

    Commands:
        - show MongoDB
        - use dbname
        - db-courses.find()
        - db-courses.insert()
    
    Steps:
    Connect to MongoDB
    Create a new database
    Create a collection
    Insert documents (Create)
    Read documents (Retrieve)
    Update documents
    Delete documents
    
    1. Create Database  
        - use myDatabase

    2. Create a Collection
        - db.createCollection("myCollection")

    3. Insert document in the Database  
        - db.myCollection.insertOne({ name: "John Doe", age: 25, profession: "Engineer" })

        - To insert multiple objects:
            db.myCollection.insertMany([
             { name: "Alice", age: 30, profession: "Doctor" },
                { name: "Bob", age: 22, profession: "Designer" }
            ])
    4. View the Documents in the Collection
        - db.myCollection.find()
        - db.myCollection.find().pretty()

        Read specific data: 
        - for Specific Data: 
            - db.myCollection.find({ name: "Alice" })

        - to update one document:
            - db.myCollection.updateOne(
                    { name: "Alice" }, 
                    { $set: { age: 26 } }
                )
        - to pdate multiple documents:
            - db.myCollection.updateMany(
                    { profession: "Designer" },
                    { $set: { profession: "Graphic Designer" } }
                )

        - to delete one document:
            - db.myCollection.deleteOne({ name: "Charlie" })

        - to delete multiple documents:
            - db.myCollection.deleteMany({ profession: "Graphic Designer" })


    5. Check existing Database and Collections
        - show databases
        - show collections

    6. Find documents where name is "Alice" OR age is greater than 25.
        - db.myCollection.find({
            $or: [
                { name: "Alice" },
                { age: { $gt: 25 } }
                ]
            })

    7. AND Operator
        db.myCollection.find({
            $and: [
                { name: "Alice" },
                { age: { $gt: 25 } }
            ]
        })

    8. Find documents where name is "Alice" AND age is greater than 25.
        db.myCollection.find({
            $and: [
            { name: "Alice" },
            { age: { $gt: 25 } }
        ]
        })


    9. where age is less than 25
        db.myCollection.find({ age: { $lt: 25 } })

    10. Find documents where age is not equal to 30.
        db.myCollection.find({ age: { $ne: 30 } })

    11. To add a field and return the updated document:
        db.users.findOneAndUpdate(
            { _id: ObjectId("your_document_id") }, // Filter
            { $set: { isVerified: true } }, // New field
            { returnDocument: "after" } // Returns the updated document
        )

    12. Update many documents
        db.users.updateMany(
            { organization: "QAU" }, // Filter criteria
            { $set: { status: "active" } } // New field and value
        )

    13. Add or update multiple fields at once for all matching documents:
        db.users.updateMany(
            { department: "Computer Science" }, // Filter criteria
            { $set: { status: "active", lastUpdated: new Date() } } // Fields to update
        )

    14. Remove the temporaryField from all matching documents:
        db.users.updateMany(
            { organization: "QAU" }, // Filter
            { $unset: { temporaryField: "" } } // Remove field
        )
    
    15. Remove Multiple Fields at Once
        db.users.updateMany(
            { department: "Computer Science" }, // Filter criteria
            { $unset: { temporaryField1: "", temporaryField2: "" } } // Fields to remove
        )

    16. Remove a Field from a Single Document
        db.users.updateOne(
            { _id: ObjectId("your_document_id") }, // Filter to find the document
            { $unset: { temporaryField: "" } } // Field to remove
        )
    



    -> Mongoose
        - an object data modelling(ODM) library for MongoDB and Nodejs providing highet level of abstraction.

        - Schema is created to model data.
        -