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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:

    mongod

  • Mongo Shell Access:

  mongosh
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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" }
  ]
});
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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 } }
]);
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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 });
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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"
  }
}
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Reference Example:

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

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