MongoDB Update

Master document modification and data updates in MongoDB

✏️ What is MongoDB Update?

Update operations in MongoDB allow you to modify existing documents in a collection. You can update single documents, multiple documents, or even insert new documents if they don't exist. MongoDB provides powerful update operators to modify specific fields, arrays, and nested objects efficiently. 


// Basic update operations
db.users.updateOne(
    { name: "John" },           // Filter
    { $set: { age: 30 } }       // Update
)

db.products.updateMany(
    { category: "electronics" }, // Filter multiple documents
    { $inc: { price: 10 } }     // Increase price by 10
)
3
Update Methods
20+
Update Operators
Flexible
Modifications

Update Methods

📝

updateOne()

Update single document 

db.users.updateOne(
    { _id: 1 },
    { $set: { status: "active" } }
)
📋

updateMany()

Update multiple documents 

db.products.updateMany(
    { price: { $lt: 100 } },
    { $set: { sale: true } }
)
🔄

replaceOne()

Replace entire document 

db.users.replaceOne(
    { _id: 1 },
    { name: "John", age: 25 }
)
➕

upsert

Update or insert if not exists 

db.users.updateOne(
    { email: "[email protected]" },
    { $set: { name: "New User" } },
    { upsert: true }
)

Basic Update Operations

Learn the fundamental update methods in MongoDB 

// Sample data
db.users.insertMany([
    { _id: 1, name: "Alice", age: 25, city: "New York" },
    { _id: 2, name: "Bob", age: 30, city: "London" },
    { _id: 3, name: "Charlie", age: 35, city: "Paris" }
])

// updateOne() - Updates the first matching document
db.users.updateOne(
    { name: "Alice" },              // Filter criteria
    { $set: { age: 26 } }          // Update operation
)

// updateMany() - Updates all matching documents
db.users.updateMany(
    { age: { $gte: 30 } },         // Filter: age >= 30
    { $set: { status: "senior" } }  // Update operation
)

// Check results
db.users.find().pretty()

Update Operators

MongoDB provides various operators to modify documents

🔹 Field Update Operators 

// $set - Set field value
db.users.updateOne(
    { _id: 1 },
    { $set: { email: "[email protected]", verified: true } }
)

// $unset - Remove field
db.users.updateOne(
    { _id: 1 },
    { $unset: { city: "" } }  // Removes the city field
)

// $inc - Increment numeric value
db.products.updateOne(
    { _id: 1 },
    { $inc: { price: 5, views: 1 } }  // Increase price by 5, views by 1
)

// $mul - Multiply numeric value
db.products.updateOne(
    { _id: 1 },
    { $mul: { price: 1.1 } }  // Increase price by 10%
)

// $rename - Rename field
db.users.updateMany(
    {},
    { $rename: { "name": "fullName" } }
)

🔹 Array Update Operators 

// Sample data with arrays
db.users.updateOne(
    { _id: 1 },
    { $set: { hobbies: ["reading", "swimming"], scores: [85, 90, 78] } }
)

// $push - Add element to array
db.users.updateOne(
    { _id: 1 },
    { $push: { hobbies: "cycling" } }
)

// $pull - Remove elements from array
db.users.updateOne(
    { _id: 1 },
    { $pull: { hobbies: "swimming" } }
)

// $addToSet - Add unique element to array
db.users.updateOne(
    { _id: 1 },
    { $addToSet: { hobbies: "reading" } }  // Won't add duplicate
)

// $pop - Remove first (-1) or last (1) element
db.users.updateOne(
    { _id: 1 },
    { $pop: { scores: 1 } }  // Remove last score
)

Advanced Update Operations

Complex update scenarios and techniques

🔹 Conditional Updates 

// $min - Update if new value is smaller
db.products.updateOne(
    { _id: 1 },
    { $min: { price: 50 } }  // Only update if 50 is less than current price
)

// $max - Update if new value is larger
db.users.updateOne(
    { _id: 1 },
    { $max: { highScore: 95 } }  // Only update if 95 is greater than current
)

// $currentDate - Set current date
db.users.updateOne(
    { _id: 1 },
    { $currentDate: { lastModified: true, lastLogin: { $type: "date" } } }
)

🔹 Array Element Updates 

// Update specific array element by position
db.users.updateOne(
    { _id: 1 },
    { $set: { "scores.0": 95 } }  // Update first element
)

// Update array element using $ positional operator
db.users.updateOne(
    { _id: 1, scores: 78 },
    { $set: { "scores.$": 88 } }  // Update the matched element (78 becomes 88)
)

// Update all array elements using $[]
db.users.updateOne(
    { _id: 1 },
    { $inc: { "scores.$[]": 5 } }  // Add 5 to all scores
)

// Update array elements with condition using $[identifier]
db.users.updateOne(
    { _id: 1 },
    { $set: { "scores.$[element]": 100 } },
    { arrayFilters: [{ "element": { $gte: 90 } }] }  // Set scores >= 90 to 100
)

Upsert Operations

Update existing documents or insert new ones if they don't exist 

// Basic upsert - insert if document doesn't exist
db.users.updateOne(
    { email: "[email protected]" },
    { 
        $set: { 
            name: "New User",
            age: 25,
            createdAt: new Date()
        }
    },
    { upsert: true }  // Insert if no match found
)

// Upsert with $setOnInsert - only set these fields on insert
db.products.updateOne(
    { sku: "ABC123" },
    {
        $set: { price: 29.99, inStock: true },
        $setOnInsert: { 
            createdAt: new Date(),
            category: "electronics"
        }
    },
    { upsert: true }
)

// Check the result
var result = db.users.updateOne(
    { email: "[email protected]" },
    { $set: { lastLogin: new Date() } },
    { upsert: true }
)

if (result.upsertedId) {
    print("New document created with ID: " + result.upsertedId)
} else {
    print("Existing document updated")
}

Replace Operations

Replace entire documents while keeping the same _id 

// replaceOne() - Replace entire document content
var originalDoc = db.users.findOne({ _id: 1 })
print("Original document:")
printjson(originalDoc)

// Replace with completely new document structure
db.users.replaceOne(
    { _id: 1 },
    {
        fullName: "Alice Johnson",
        contact: {
            email: "[email protected]",
            phone: "123-456-7890"
        },
        preferences: {
            theme: "dark",
            notifications: true
        },
        updatedAt: new Date()
    }
)

var newDoc = db.users.findOne({ _id: 1 })
print("Replaced document:")
printjson(newDoc)

// Note: _id remains the same, but all other fields are replaced

Update with Aggregation Pipeline

Use aggregation expressions in update operations 

// Sample data
db.orders.insertMany([
    { _id: 1, items: [{ price: 10 }, { price: 20 }, { price: 15 }] },
    { _id: 2, items: [{ price: 25 }, { price: 30 }] }
])

// Calculate total using aggregation pipeline in update
db.orders.updateMany(
    {},
    [
        {
            $set: {
                total: {
                    $sum: "$items.price"  // Calculate sum of all item prices
                },
                itemCount: { $size: "$items" },
                updatedAt: new Date()
            }
        }
    ]
)

// Update based on existing field values
db.users.updateMany(
    {},
    [
        {
            $set: {
                ageGroup: {
                    $switch: {
                        branches: [
                            { case: { $lt: ["$age", 18] }, then: "minor" },
                            { case: { $lt: ["$age", 65] }, then: "adult" },
                            { case: { $gte: ["$age", 65] }, then: "senior" }
                        ],
                        default: "unknown"
                    }
                }
            }
        }
    ]
)

// Check results
db.orders.find().pretty()
db.users.find({}, { name: 1, age: 1, ageGroup: 1 }).pretty()

Practical Update Examples

Real-world update scenarios and solutions 

// Example 1: User profile update
function updateUserProfile(userId, profileData) {
    var result = db.users.updateOne(
        { _id: userId },
        {
            $set: {
                ...profileData,
                lastModified: new Date()
            }
        }
    )
    
    if (result.matchedCount === 0) {
        print("User not found")
        return false
    }
    
    print("Profile updated successfully")
    return true
}

// Example 2: Inventory management
function updateInventory(productId, quantityChange) {
    var result = db.products.updateOne(
        { 
            _id: productId,
            stock: { $gte: Math.abs(quantityChange) }  // Ensure sufficient stock
        },
        {
            $inc: { stock: quantityChange },
            $set: { lastUpdated: new Date() }
        }
    )
    
    if (result.matchedCount === 0) {
        print("Product not found or insufficient stock")
        return false
    }
    
    print("Inventory updated successfully")
    return true
}

// Example 3: Bulk price update with conditions
function updatePricesByCategory(category, discountPercent) {
    var result = db.products.updateMany(
        { category: category },
        [
            {
                $set: {
                    originalPrice: "$price",  // Store original price
                    price: {
                        $multiply: [
                            "$price",
                            { $subtract: [1, discountPercent / 100] }
                        ]
                    },
                    discountApplied: discountPercent,
                    saleStartDate: new Date()
                }
            }
        ]
    )
    
    print("Updated " + result.modifiedCount + " products in category: " + category)
    return result.modifiedCount
}

// Usage examples
updateUserProfile(1, { email: "[email protected]", phone: "555-0123" })
updateInventory(101, -5)  // Reduce stock by 5
updatePricesByCategory("electronics", 15)  // 15% discount

🧠 Test Your Knowledge

Which operator is used to increment a numeric field?

What happens when you use upsert: true and no document matches?

Which method updates only the first matching document?