DevCorner

Posted on Feb 20

MongoDB One-Stop Solution: Complete Guide with Cheatsheet

Introduction

MongoDB is a popular NoSQL database known for its flexible document-based model, scalability, and powerful querying capabilities. Whether you are a beginner or an experienced developer, this comprehensive guide and cheatsheet will serve as a one-stop solution for mastering MongoDB.

1. Key MongoDB Concepts

Concept	Description
Database	A container for collections.
Collection	A group of documents (similar to a table in RDBMS).
Document	A JSON-like object (key-value pairs, dynamic schema).
Field	A key-value pair in a document.
Index	Improves the speed of data retrieval.
Aggregation	Used for complex data processing and transformation.
Replication	Copies data across multiple servers for fault tolerance.
Sharding	Splits data across multiple servers to handle large datasets.

2. Setting Up MongoDB

Installation

Windows / Linux / macOS:
- Download from MongoDB Official Site.
- Follow installation instructions.
- Start the service:
```
mongod
```
Mongo Shell Access:

  mongosh

3. Basic MongoDB Commands

Database Operations

Command	Description
`show dbs`	List all databases.
`use <database>`	Switch to a database.
`db.createCollection('users')`	Create a collection.
`db.dropDatabase()`	Drop the current database.

Collection Operations

Command	Description
`db.users.insertOne({...})`	Insert a single document.
`db.users.insertMany([{...}, {...}])`	Insert multiple documents.
`db.users.find()`	Fetch all documents.
`db.users.find({name: "John"})`	Query documents with conditions.
`db.users.updateOne({condition}, {$set: {key: value}})`	Update a document.
`db.users.deleteOne({name: "John"})`	Delete a single document.
`db.users.deleteMany({age: {$gt: 30}})`	Delete multiple documents.

4. Advanced Querying

Query	Description
`$gt`, `$lt`, `$gte`, `$lte`	Comparison operators (greater, less, etc.)
`$in`, `$nin`	Matches values in a set.
`$and`, `$or`, `$not`	Logical operators.
`$exists`, `$type`	Field existence and type check.
`$regex`	Pattern matching.

Example:

db.users.find({
  $and: [
    { age: { $gte: 25 } },
    { city: "New York" }
  ]
});

5. Aggregation Framework

Used for advanced data analysis and processing.

Stage	Description
`$match`	Filters documents.
`$group`	Groups documents by a field.
`$sort`	Sorts documents.
`$limit`	Limits the number of documents.
`$project`	Reshapes documents.

Example:

db.sales.aggregate([
  { $match: { status: "Completed" } },
  { $group: { _id: "$product", total: { $sum: "$amount" } } },
  { $sort: { total: -1 } }
]);

6. Indexing

Type	Description
Single Field Index	Index on a single field.
Compound Index	Index on multiple fields.
Text Index	Full-text search support.

Create Index:

db.users.createIndex({ name: 1 });

7. Relationships in MongoDB

Approach	Description
Embedded Documents	Store related data in a single document.
References	Store references (ObjectId) to other documents.

Embedded Example:

{
  name: "John Doe",
  address: {
    city: "New York",
    zip: "10001"
  }
}

Reference Example:

{
  name: "John Doe",
  addressId: ObjectId("603cf82a5e8b7a2e9c1f1f1f")
}

8. Data Modeling Best Practices

Design according to application query patterns.
Favor embedded documents for fast reads.
Use references for complex relationships or large datasets.
Index frequently queried fields.

9. Backup and Restore

Command	Description
`mongodump --out /backup`	Backup all databases.
`mongorestore /backup`	Restore from backup.

10. MongoDB Compass (GUI Tool)

Download: MongoDB Compass
Connect using connection string.
Visualize data and perform queries.

11. Performance Optimization Tips

Use proper indexing.
Avoid $where and complex JavaScript operations.
Limit the result set using .limit() and .skip().
Use aggregation pipelines for heavy data processing.

12. Common Errors & Solutions

Error	Cause/ Solution
`E11000 duplicate key error`	Unique index conflict, check for duplicates.
`Network Error`	Check server connection or firewall.
`MongoParseError`	Invalid connection string format.

13. Quick MongoDB Cheatsheet

// Database Operations
show dbs;
use mydb;
db.dropDatabase();

// Collection Operations
db.createCollection('users');
db.users.drop();

// CRUD Operations
db.users.insertOne({name: "Alice", age: 25});
db.users.find({age: {$gte: 25}});
db.users.updateOne({name: "Alice"}, {$set: {age: 26}});
db.users.deleteOne({name: "Alice"});

// Aggregation
db.users.aggregate([
  { $match: { age: { $gte: 25 } } },
  { $group: { _id: "$city", count: { $sum: 1 } } }
]);

// Indexing
db.users.createIndex({name: 1});
db.users.getIndexes();

// Backup & Restore
mongodump --out /backup;
mongorestore /backup;

14. Useful Resources

Final Thoughts

Mastering MongoDB involves understanding its flexible document model, using aggregation for powerful data analysis, and optimizing performance with indexing. With this guide and cheatsheet, you’re equipped to handle MongoDB confidently in your development projects.

Happy Coding!

Forem