Unit 01

Definition of NoSQL

NoSQL stands for “Not Only SQL.” It refers to database management systems that store and retrieve data using models other than the traditional row-and-column table structure of relational databases.

NoSQL databases generally provide a flexible/schema-less structure, support horizontal scaling, handle large amounts of unstructured data, and are designed for high-speed distributed systems.

Types of NoSQL Databases

There are four major types:

Advantages (Pros) of NoSQL

Disadvantages (Cons) of NoSQL

NoSQL databases provide several architectural features that make them suitable for large-scale, distributed, and flexible applications.

CRUD stands for Create, Read, Update, and Delete. These are the four basic operations used to manage data in MongoDB.

db.collectionName.insertOne(document)

db.students.insertOne({
    name: "Riya Shah",
    age: 20,
    course: "BCA"
})

db.students.insertMany([
    { name: "Aman", age: 21 },
    { name: "Priya", age: 22 }
])

db.collectionName.find({ condition })

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

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

db.students.find({ age: { $gt: 18 } })

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

db.students.updateMany(
    { course: "BCA" },
    { $set: { year: 2026 } }
)

db.students.deleteOne(
    { name: "Karan Joshi" }
)

db.students.deleteMany(
    { course: "BCA" }
)

The Aggregation Framework in MongoDB is used to process documents and return computed results. It works using an aggregation pipeline, where documents pass through a sequence of stages. Each stage performs an operation and passes its output to the next stage.

It is useful for operations such as filtering, grouping, calculating totals/averages, reshaping documents, sorting, and joining collections.

db.collection.aggregate([
    { stage1 },
    { stage2 },
    ...
])

db.students.aggregate([
    { $match: { course: "BCA" } },
    { $sort: { marks: -1 } },
    { $limit: 2 },
    { $project: { _id: 0, name: 1, marks: 1 } }
])

Update operators in MongoDB are used with methods such as updateOne() and updateMany() to modify specific fields of existing documents without replacing the entire document.

SQL databases are relational databases that store data in structured tables and rows, whereas NoSQL databases can store data using documents, key-value pairs, graphs, or column-family models.

Explanation of Major Differences