Module - 2: Basic Operations in MongoDB

Lesson 5: NoSQL Models

 

 

Understanding NoSQL concepts:

  • Flexible Schema: NoSQL databases, like MongoDB, embrace a schema-less approach, allowing for dynamic and flexible data structures. This flexibility facilitates easy adjustments to data models without imposing a predefined schema on all documents.

  Example: Suppose an application adds new fields to a user profile. In MongoDB, each document can have different fields, reflecting the changing requirements without altering the entire database structure.


  • Scalability: NoSQL databases are built to handle horizontal scalability, making it simpler to distribute data across multiple servers or nodes, ensuring high availability and performance as data volumes grow.

  Example: MongoDB's horizontal scaling feature, known as sharding, partitions data across shards, distributing the load and enhancing performance.


Comparison between NoSQL and relational databases:


  • Data Structure: In contrast to relational databases with rigid tabular structures, NoSQL databases like MongoDB store data as flexible documents. These documents can hold nested fields, arrays, and different data types within a single record.

  For Example: Storing a user's address, contact details, and preferences within a single document in MongoDB compared to distributing this information across multiple tables in a relational database.


  • Query Language: While SQL is the standard query language for relational databases, NoSQL databases often use different query languages or APIs tailored to their data models.

  For Example: MongoDB employs a query language using JSON-like syntax, allowing users to perform various operations such as filtering, projecting, and aggregating data in a document-centric manner.


NoSQL data modeling best practices:


  • Denormalization: NoSQL databases often encourage denormalization by combining related data into a single document, reducing the need for joins and optimizing read performance.

  Example: Embedding comments within a blog post document in MongoDB, eliminating the need for a separate 'comments' collection.


  • Avoiding Joins: NoSQL databases discourage complex join operations by either embedding related data or using references between documents, simplifying data retrieval and improving performance.

  Example: Storing user roles and permissions within a user document, reducing the need to fetch this information from separate tables in a relational database.


 Lesson 6: CRUD Operations: insert, insertOne, insertMany

 

 

Inserting documents into MongoDB:

Inserting documents into MongoDB is straightforward using commands like `insertOne()` or `insertMany()`. With a flexible schema, MongoDB allows easy addition of single or multiple documents into collections. Using JSON-like syntax, documents are inserted swiftly, accommodating diverse data types and structures. For instance, `insertOne()` adds a single document, while `insertMany()` bulk-inserts multiple records efficiently, simplifying data management in MongoDB collections.


- insert(), insertOne(), insertMany(): These MongoDB methods facilitate the insertion of documents into collections. `insert()` is deprecated, and `insertOne()` and `insertMany()` are preferred methods for single and multiple document insertions.

  Example: Inserting a single user document into a 'users' collection using `insertOne()`.


```javascript

db.users.insertOne({ name: "Alice", age: 25 });

```


- Syntax and usage examples for CRUD operations: Demonstrations showcasing the syntax and usage of methods like `insertOne()` and `insertMany()` to add single or multiple documents into collections.

  Example: Adding multiple users to the 'users' collection using `insertMany()`.


```javascript

db.users.insertMany([

    { name: "Bob", age: 30 },

    { name: "Charlie", age: 28 }

]);

```


 Lesson 7: Querying and Updating Documents

 

 

Querying and updating documents in MongoDB involves powerful methods like find() and updateOne(). Using a rich query language resembling JSON, find() retrieves documents based on specified criteria, allowing precise data extraction. Meanwhile, updateOne() enables targeted updates to individual documents, providing flexibility in modifying existing data without altering the entire collection. These operations empower users to efficiently retrieve and manipulate data, ensuring accurate and tailored modifications within MongoDB collections.

Querying documents using find() and findOne():


- find() and findOne(): These methods retrieve documents from collections based on specified query criteria. `find()` returns multiple matching documents, while `findOne()` fetches the first document that matches the query.

  Example: Using `find()` to retrieve users older than 25 from the 'users' collection.


```javascript

db.users.find({ age: { $gt: 25 } });

```


Updating documents using updateOne() and updateMany():


- updateOne() and updateMany(): These methods modify existing documents in collections. `updateOne()` updates a single document, while `updateMany()` updates multiple documents.

  Example: Using `updateMany()` to increment the age of users younger than 30 in the 'users' collection.


```javascript

db.users.updateMany({ age: { $lt: 30 } }, { $inc: { age: 1 } });

```

 Lesson 8: Replace and Delete Documents

 

 

Replacing documents with replaceOne():


replaceOne(): This method replaces a single document in a collection with another document.

  Example: Using `replaceOne()` to update a user's information in the 'users' collection.


```javascript

db.users.replaceOne({ name: "Alice" }, { name: "Alicia", age: 27 });

```

Deleting documents using deleteOne() and deleteMany():


deleteOne() and deleteMany(): These methods remove documents from collections. `deleteOne()` removes a single document, while `deleteMany()` removes multiple documents.

  Example: Using `deleteMany()` to remove users older than or equal to 30 from the 'users' collection.


```javascript

db.users.deleteMany({ age: { $gte: 30 } });

```

Mastering these MongoDB operations enables users to efficiently manage data, perform queries, updates, and deletions, thereby harnessing the full potential of MongoDB in handling diverse datasets and applications.


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