MongoDB Find

Query and retrieve documents from collections

🔍 Finding Documents

Finding documents in MongoDB means querying collections to retrieve data. Use find() to get multiple documents or findOne() to retrieve a single document matching your search criteria efficiently. 


// Find all documents
db.users.find()

// Find one document
db.users.findOne({ name: "Alice" })

// Find with conditions
db.users.find({ age: { $gt: 25 } })

Find Methods

MongoDB provides powerful query methods to search and retrieve documents. You can find all documents, find specific ones, or use advanced filters to get exactly what you need.

📋

find()

Retrieve all matching documents 

db.users.find()
1️⃣

findOne()

Get first matching document 

db.users.findOne({...})
🎯

Query Filters

Search with specific conditions 

{ age: { $gt: 25 } }
📊

Projection

Select specific fields to return 

{ name: 1, age: 1 }

🔹 Find All Documents

Use find() without parameters to retrieve all documents in a collection: 

// Find all users
db.users.find()

// Find all and format output
db.users.find().pretty()

Output:

{ _id: 1, name: "Alice", age: 25 }

{ _id: 2, name: "Bob", age: 30 }

{ _id: 3, name: "Carol", age: 28 }

🔹 Find One Document

Use findOne() to retrieve the first document that matches your query: 

// Find first user
db.users.findOne()

// Find specific user by name
db.users.findOne({ name: "Alice" })

// Find by _id
db.users.findOne({ _id: 1 })

Output:

{ _id: 1, name: "Alice", age: 25, city: "New York" }

🔹 Find with Query Filters

Add conditions to find specific documents: 

// Find users older than 25
db.users.find({ age: { $gt: 25 } })

// Find users from specific city
db.users.find({ city: "New York" })

// Find with multiple conditions
db.users.find({ 
    age: { $gte: 25 },
    city: "Boston"
})

Output:

{ _id: 2, name: "Bob", age: 30, city: "Boston" }

{ _id: 3, name: "Carol", age: 28, city: "Boston" }

🔹 Common Query Operators

MongoDB provides operators for advanced queries:

Comparison Operators:

  • $eq: Equal to
  • $ne: Not equal to
  • $gt: Greater than
  • $gte: Greater than or equal
  • $lt: Less than
  • $lte: Less than or equal
  • $in: Matches any value in array 
// Greater than
db.products.find({ price: { $gt: 100 } })

// In array
db.users.find({ city: { $in: ["Boston", "New York"] } })

// Not equal
db.orders.find({ status: { $ne: "cancelled" } })

🔹 Logical Operators

Combine multiple conditions with logical operators: 

// AND condition (implicit)
db.users.find({ 
    age: { $gt: 25 },
    city: "Boston"
})

// OR condition
db.users.find({
    $or: [
        { age: { $lt: 25 } },
        { city: "New York" }
    ]
})

// NOT condition
db.products.find({
    price: { $not: { $gt: 100 } }
})

Output:

{ _id: 1, name: "Alice", age: 22, city: "New York" }

{ _id: 4, name: "David", age: 35, city: "New York" }

🔹 Projection (Select Fields)

Choose which fields to include or exclude in results: 

// Include only name and age (exclude _id)
db.users.find(
    {},
    { name: 1, age: 1, _id: 0 }
)

// Exclude specific fields
db.users.find(
    {},
    { password: 0, email: 0 }
)

// Find with filter and projection
db.users.find(
    { age: { $gt: 25 } },
    { name: 1, city: 1 }
)

Output:

{ name: "Bob", age: 30 }

{ name: "Carol", age: 28 }

🔹 Sorting and Limiting

Sort results and limit the number of documents returned: 

// Sort by age (ascending)
db.users.find().sort({ age: 1 })

// Sort by age (descending)
db.users.find().sort({ age: -1 })

// Limit results to 5 documents
db.users.find().limit(5)

// Skip first 10 and get next 5
db.users.find().skip(10).limit(5)

// Combine: sort, skip, limit
db.products.find()
    .sort({ price: -1 })
    .skip(0)
    .limit(10)

Output:

{ _id: 2, name: "Bob", age: 30 }

{ _id: 3, name: "Carol", age: 28 }

{ _id: 1, name: "Alice", age: 25 }

🔹 Count Documents

Count how many documents match your query: 

// Count all documents
db.users.countDocuments()

// Count with filter
db.users.countDocuments({ age: { $gt: 25 } })

// Estimated count (faster, less accurate)
db.users.estimatedDocumentCount()

Output:

Total users: 150

Users over 25: 87

🔹 Complete Example

Here's a practical example combining various find operations: 

// Switch to database
use storeDB

// Find all products
db.products.find()

// Find expensive products
db.products.find({ price: { $gte: 500 } })

// Find electronics under $1000
db.products.find({
    category: "Electronics",
    price: { $lt: 1000 }
})

// Get top 5 most expensive products
db.products.find()
    .sort({ price: -1 })
    .limit(5)
    .projection({ name: 1, price: 1 })

// Find products in stock
db.products.find({
    stock: { $gt: 0 }
}).count()

// Search by multiple categories
db.products.find({
    category: { $in: ["Electronics", "Computers"] },
    price: { $lte: 2000 }
}).sort({ price: 1 })

Output:

{ name: "Gaming Mouse", price: 79 }

{ name: "Mechanical Keyboard", price: 149 }

{ name: "Monitor 27\"", price: 399 }

{ name: "Laptop Pro", price: 1299 }

🧠 Test Your Knowledge

Which operator would you use to find documents where age is greater than 25?