30. What is NoSQL? What are its advantages and disadvantages?

NoSQL is a type of database that does not use the traditional relational model (SQL). NoSQL offers flexible data structures and scalability, making it a suitable choice for applications with large amounts of data and dynamic schemas.

Advantages of NoSQL:

1. Scalability: NoSQL is designed for easy horizontal scaling, allowing it to handle large amounts of data and high traffic.
2. Flexible schemas: NoSQL allows storing data in flexible, unstructured formats such as JSON documents, making it easier to manage changing data requirements.
3. High performance: NoSQL can offer better performance in high read/write operations applications, optimized for specific data types.
4. Ease of data management: NoSQL often provides built-in mechanisms for replication and sharding, simplifying large-scale data management.

Disadvantages of NoSQL:

1. Lack of standardization: There are many different types of NoSQL databases (document, key-value, graph, column), which can make choosing the right tool difficult.
2. Limited transactional support: Many NoSQL databases do not offer full ACID compliance, which can be problematic in applications requiring high data integrity.
3. Tendency to complexity: Flexible data schemas can lead to complexity in managing and ensuring data consistency.

Example of using a NoSQL database (MongoDB):

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017';
const dbName = 'mydatabase';

MongoClient.connect(url, { useNewUrlParser: true, useUnifiedTopology: true }, (err, client) => {
  if (err) throw err;
  const db = client.db(dbName);
  const collection = db.collection('documents');
  collection.insertOne({ name: 'John', age: 30 }, (err, result) => {
    if (err) throw err;
    console.log('Document inserted');
    client.close();
  });
});

NoSQL is a powerful tool for applications requiring flexibility and scalability but requires careful management and appropriate tool selection.