CRUD Operations

NoSQL CRUD Operations: Your Database Kitchen Adventure 🍳

Imagine you have a magical recipe box where you can store, find, change, and remove recipe cards anytime. That’s exactly what CRUD operations do in NoSQL databases! CRUD stands for Create, Read, Update, Delete — the four superpowers that let you manage your data.

Let’s explore each superpower with our recipe box!

1. Create and Insert Operations: Adding New Recipes

Think of it like: Writing a new recipe card and placing it in your box.

When you create or insert, you’re adding a brand new document (like a recipe card) to your collection (the recipe box).

How It Works

In NoSQL (like MongoDB), you insert documents like this:

// Add ONE recipe
db.recipes.insertOne({
  name: "Chocolate Cake",
  ingredients: ["flour", "sugar", "cocoa"],
  time: 45
})

// Add MANY recipes at once
db.recipes.insertMany([
  { name: "Cookies", time: 20 },
  { name: "Brownies", time: 30 }
])

What happens?

• The database gives each document a unique ID (like a barcode on your recipe card)
• Your new data is now safely stored!

Key Points

• insertOne() — adds one document
• insertMany() — adds multiple documents at once
• Each document automatically gets a unique _id

2. Read and Query Operations: Finding Your Recipes

Think of it like: Looking through your recipe box to find what you want.

Reading is how you ask questions to your database and get answers back.

Simple Queries

// Find ALL recipes
db.recipes.find()

// Find ONE specific recipe
db.recipes.findOne({ name: "Chocolate Cake" })

// Find recipes that take less than 30 minutes
db.recipes.find({ time: { $lt: 30 } })

Query Operators (Your Search Tools)

Real example: “Show me all recipes with chocolate that take under an hour”

db.recipes.find({
  ingredients: "chocolate",
  time: { $lt: 60 }
})

3. Document Projections: Picking What to Show

Think of it like: When someone asks for a recipe, you only read them the parts they need — not the whole card!

Projections let you choose which fields to include or exclude in your results.

How Projections Work

// Show ONLY name and time (exclude everything else)
db.recipes.find(
  {},
  { name: 1, time: 1 }
)

// Show everything EXCEPT ingredients
db.recipes.find(
  {},
  { ingredients: 0 }
)

The rules:

• 1 means include this field
• 0 means exclude this field
• The _id field shows by default (use _id: 0 to hide it)

Why Use Projections?

• Faster: Less data to transfer
• Cleaner: Only get what you need
• Safer: Hide sensitive information

// Perfect example: Get recipe names only
db.recipes.find({}, { name: 1, _id: 0 })
// Result: [{ name: "Cake" }, { name: "Cookies" }]

4. Update Operations: Changing Your Recipes

Think of it like: Erasing something on your recipe card and writing something new.

Updates let you modify existing documents without deleting and re-creating them.

Update Commands

// Update ONE recipe
db.recipes.updateOne(
  { name: "Chocolate Cake" },
  { $set: { time: 50 } }
)

// Update MANY recipes
db.recipes.updateMany(
  { time: { $lt: 20 } },
  { $set: { difficulty: "easy" } }
)

Update Operators (Your Editing Tools)

Real Example

// Add a new ingredient to our cake
db.recipes.updateOne(
  { name: "Chocolate Cake" },
  { $push: { ingredients: "vanilla" } }
)

5. Delete Operations: Removing Recipes

Think of it like: Taking a recipe card out of your box and throwing it away.

Delete operations permanently remove documents from your collection.

Delete Commands

// Delete ONE recipe
db.recipes.deleteOne({ name: "Old Recipe" })

// Delete MANY recipes
db.recipes.deleteMany({ time: { $gt: 120 } })

// Delete ALL recipes (careful!)
db.recipes.deleteMany({})

Important!

• deleteOne() — removes the first matching document
• deleteMany() — removes ALL matching documents
• There’s no undo! Once deleted, it’s gone forever

// Delete all recipes without ratings
db.recipes.deleteMany({ rating: { $exists: false } })

6. Tombstones: The Ghost Markers

Think of it like: Instead of throwing away a recipe, you put a “DO NOT USE” sticker on it.

A tombstone is a marker that says “this data was deleted” without actually removing it immediately.

Why Use Tombstones?

graph TD
    A["Delete Request"] --> B{Hard Delete?}
    B -->|Yes| C["Data Gone Forever"]
    B -->|No - Soft Delete| D["Add Tombstone"]
    D --> E["Data Hidden But Recoverable"]
    E --> F["Clean Up Later"]

How Tombstones Work

// Instead of deleting, mark as deleted
db.recipes.updateOne(
  { name: "Old Cake" },
  {
    $set: {
      deleted: true,
      deletedAt: new Date()
    }
  }
)

// Query excludes tombstoned items
db.recipes.find({ deleted: { $ne: true } })

Tombstone Benefits

• Undo mistakes: Can recover “deleted” data
• Audit trail: Know what was deleted and when
• Sync systems: Tells other databases about deletions
• Compliance: Some laws require keeping records

7. Upsert Operations: The Smart Combo

Think of it like: “If the recipe exists, update it. If not, create a new one!”

Upsert = Update + Insert combined into one smart operation.

How Upsert Works

graph TD
    A["Upsert Command"] --> B{Document Exists?}
    B -->|Yes| C["Update It"]
    B -->|No| D["Insert New One"]
    C --> E["Done!"]
    D --> E

Upsert in Action

// The magic upsert option
db.recipes.updateOne(
  { name: "Mystery Dish" },
  { $set: { time: 25, category: "quick" } },
  { upsert: true }  // <-- The magic!
)

What happens:

• If “Mystery Dish” exists → it gets updated
• If “Mystery Dish” doesn’t exist → a new document is created

Why Upsert is Amazing

• One command: No need to check if document exists first
• No duplicates: Prevents accidentally creating copies
• Atomic: Happens as one operation (safe and fast)

// Perfect for counters and tracking
db.pageViews.updateOne(
  { page: "/home" },
  { $inc: { count: 1 } },
  { upsert: true }
)
// First visit: creates { page: "/home", count: 1 }
// Second visit: updates to { page: "/home", count: 2 }

Summary: Your CRUD Superpowers

Remember This!

graph LR
    C["CREATE"] --> R["READ"]
    R --> U["UPDATE"]
    U --> D["DELETE"]
    D --> C
    style C fill:#4CAF50,color:#fff
    style R fill:#2196F3,color:#fff
    style U fill:#FF9800,color:#fff
    style D fill:#f44336,color:#fff

You now have all four superpowers:

1. 🟢 Create — Add new data
2. 🔵 Read — Find and retrieve data
3. 🟠 Update — Change existing data
4. 🔴 Delete — Remove data

Plus the bonus powers:

• 📋 Projections — Show only what you need
• 👻 Tombstones — Soft delete with recovery
• ⚡ Upsert — Smart update-or-create

Congratulations! You’re now a CRUD master! 🎉