MongoDB Crash Course

Introduction

This tutorial serves as a comprehensive guide to MongoDB, a popular NoSQL database that is easy to use and flexible for various projects. We will cover essential concepts, including basic commands, data manipulation, querying, updating, and deleting records. By the end of this guide, you'll have a solid understanding of MongoDB's core functionalities.

Chapter 1: Basic Commands

To get started with MongoDB, ensure you have it installed on your system. Follow these steps:

1. Install MongoDB:

   • Visit the MongoDB Community Edition download page.
   • Choose your operating system and follow the installation instructions.

2. Install MongoDB Shell (sh):

   • Download the MongoDB Shell appropriate for your operating system.
   • Follow the installation steps provided.

3. Open the Terminal:

   • Launch your terminal and type sh to enter the MongoDB Shell.

4. Basic Commands:

   • To view existing databases, type:

     show dbs
     

   • To switch to an existing database or create a new one, use:

     use appdb
     

   • To view collections within the current database, type:

     show collections
     

   • To delete a database, use:

     db.dropDatabase()
     

   • To clear the terminal screen, type:

     cls
     

   • To exit the shell, simply type:

     exit
     

Chapter 2: Insert Commands

Inserting data into MongoDB is straightforward. Follow these steps:

1. Insert a Single Record:

   • To insert a user, use:

     db.users.insertOne({ name: "John" })
     

2. View Records:

   • To see the inserted records, type:

     db.users.find()
     

3. Insert Multiple Records:

   • To insert multiple users at once, use:

     db.users.insertMany([{ name: "Jill" }, { name: "Mike" }])
     

4. Insert Complex Documents:

   • You can insert documents with nested objects and arrays:

     db.users.insertOne({
       name: "Sally",
       age: 19,
       address: { street: "987 North Street" },
       hobbies: ["running"]
     })
     

Chapter 3: Basic Query Commands

Querying your data allows you to retrieve specific records. Here’s how:

1. Find All Records:

   • To fetch all records from the users collection:

     db.users.find()
     

2. Limit Results:

   • To limit the number of results:

     db.users.find().limit(2)
     

3. Sort Results:

   • To sort by name in alphabetical order:

     db.users.find().sort({ name: 1 })
     

4. Complex Queries:

   • To find users by specific criteria:

     db.users.find({ name: "Kyle" })
     

Chapter 4: Complex Query Commands

For more complex queries, use the following techniques:

1. Use Comparison Operators:

   • For age greater than a specific value:

     db.users.find({ age: { $gt: 20 } })
     

2. Combine Queries:

   • To find users with conditions:

     db.users.find({ age: { $gte: 20, $lte: 40 } })
     

3. Logical Operators:

   • To use logical conditions:

     db.users.find({ $or: [{ age: { $lte: 20 } }, { name: "Kyle" }] })
     

Chapter 5: Update Commands

Updating records in MongoDB is essential for maintaining data integrity. Here’s how to do it:

1. Update a Single Record:

   • To update a specific user’s age:

     db.users.updateOne({ name: "Kyle" }, { $set: { age: 27 } })
     

2. Increment a Value:

   • To increment a user’s age by 1:

     db.users.updateOne({ name: "Kyle" }, { $inc: { age: 1 } })
     

3. Remove a Field:

   • To unset a specific field:

     db.users.updateOne({ name: "Kyle" }, { $unset: { age: "" } })
     

4. Update Multiple Records:

   • To update all users with a specific condition:

     db.users.updateMany({ address: { $exists: true } }, { $unset: { address: "" } })
     

Chapter 6: Delete Commands

Deleting records is straightforward. Here’s how:

1. Delete a Single Record:

   • To delete a specific user:

     db.users.deleteOne({ name: "John" })
     

2. Delete Multiple Records:

   • To delete all users without an age:

     db.users.deleteMany({ age: { $exists: false } })
     

Conclusion

In this tutorial, we've covered the essential commands and operations you need to work effectively with MongoDB. You now have the foundational skills to create, read, update, and delete records in a MongoDB database. For further learning, consider exploring advanced topics or practical applications of MongoDB in your projects. Happy coding!