Queries
Basic Find Queries
Simple Find Operations
// Find all documents
db.users.find()
// Find with pretty formatting
db.users.find().pretty()
// Find one document
db.users.findOne()
// Find with limit
db.users.find().limit(10)
// Find with skip
db.users.find().skip(5)
// Find with sort
db.users.find().sort({ name: 1 }) // ascending
db.users.find().sort({ age: -1 }) // descendingFind with Filters
// Find by exact match
db.users.find({ name: "John Doe" })
// Find by multiple conditions
db.users.find({
age: { $gte: 25 },
city: "New York"
})
// Find by field existence
db.users.find({ email: { $exists: true } })
// Find by field type
db.users.find({ age: { $type: "number" } })
// Find by null values
db.users.find({ middleName: null })Comparison Operators
Basic Comparison
// Equal
db.users.find({ age: 30 })
// Greater than
db.users.find({ age: { $gt: 25 } })
// Less than
db.users.find({ age: { $lt: 30 } })
// Greater than or equal
db.users.find({ age: { $gte: 25 } })
// Less than or equal
db.users.find({ age: { $lte: 30 } })
// Not equal
db.users.find({ age: { $ne: 30 } })Array Comparison
// In array
db.users.find({ age: { $in: [25, 30, 35] } })
// Not in array
db.users.find({ age: { $nin: [25, 30, 35] } })
// Array contains element
db.users.find({ tags: "developer" })
// Array contains all elements
db.users.find({ tags: { $all: ["javascript", "mongodb"] } })
// Array size
db.users.find({ tags: { $size: 3 } })
// Array element at position
db.users.find({ "tags.0": "javascript" })Date Comparison
// Date range
db.users.find({
createdAt: {
$gte: new Date("2023-01-01"),
$lt: new Date("2023-12-31")
}
})
// Date comparison with current time
db.users.find({
lastLogin: { $lt: new Date(Date.now() - 7 * 24 * 60 * 60 * 1000) }
})
// Date field exists
db.users.find({ createdAt: { $exists: true } })Logical Operators
AND Operations
// Implicit AND
db.users.find({
age: { $gte: 25 },
city: "New York",
status: "active"
})
// Explicit AND
db.users.find({
$and: [
{ age: { $gte: 25 } },
{ city: "New York" },
{ status: "active" }
]
})OR Operations
// OR operator
db.users.find({
$or: [
{ city: "New York" },
{ city: "Los Angeles" }
]
})
// Multiple OR conditions
db.users.find({
$or: [
{ age: { $lt: 25 } },
{ age: { $gt: 65 } },
{ status: "vip" }
]
})NOT Operations
// NOT operator
db.users.find({ age: { $not: { $lt: 18 } } })
// NOT with regex
db.users.find({ email: { $not: /gmail\.com$/ } })
// NOT with multiple conditions
db.users.find({
$not: {
$or: [
{ status: "inactive" },
{ age: { $lt: 18 } }
]
}
})NOR Operations
// NOR operator (neither condition is true)
db.users.find({
$nor: [
{ age: { $lt: 18 } },
{ status: "inactive" }
]
})Element Operators
Field Existence
// Field exists
db.users.find({ email: { $exists: true } })
// Field does not exist
db.users.find({ middleName: { $exists: false } })
// Field exists and is not null
db.users.find({ email: { $exists: true, $ne: null } })Field Type
// Field is string
db.users.find({ name: { $type: "string" } })
// Field is number
db.users.find({ age: { $type: "number" } })
// Field is array
db.users.find({ tags: { $type: "array" } })
// Field is object
db.users.find({ profile: { $type: "object" } })
// Field is date
db.users.find({ createdAt: { $type: "date" } })Evaluation Operators
Regex Patterns
// Case insensitive regex
db.users.find({ name: { $regex: /john/i } })
// Case sensitive regex
db.users.find({ email: { $regex: /^john/ } })
// Regex with options
db.users.find({ name: { $regex: "john", $options: "i" } })
// Complex regex patterns
db.users.find({ email: { $regex: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/ } })Text Search
// Text search (requires text index)
db.users.find({ $text: { $search: "john developer" } })
// Text search with score
db.users.find({ $text: { $search: "javascript" } })
.sort({ score: { $meta: "textScore" } })
// Text search with language
db.users.find({ $text: { $search: "developer", $language: "english" } })Expression Evaluation
// Using $expr for field comparisons
db.users.find({
$expr: { $gt: ["$age", "$minAge"] }
})
// Using $expr with arithmetic
db.users.find({
$expr: { $gt: [{ $add: ["$baseSalary", "$bonus"] }, 100000] }
})
// Using $expr with conditional
db.users.find({
$expr: {
$cond: {
if: { $gte: ["$age", 18] },
then: { $gte: ["$salary", 50000] },
else: false
}
}
})Array Queries
Array Element Queries
// Array contains element
db.users.find({ skills: "JavaScript" })
// Array contains multiple elements
db.users.find({ skills: { $all: ["JavaScript", "MongoDB"] } })
// Array element matches condition
db.users.find({ "skills": { $elemMatch: { $regex: /^Java/ } } })
// Array element at specific position
db.users.find({ "skills.0": "JavaScript" })
// Array size
db.users.find({ skills: { $size: 3 } })Array Element Matching
// Array element with multiple conditions
db.users.find({
"skills": {
$elemMatch: {
$regex: /^Java/,
$ne: "JavaScript"
}
}
})
// Array of objects
db.users.find({
"projects": {
$elemMatch: {
name: "Web App",
status: "completed"
}
}
})Array Operations
// Array with specific size
db.users.find({ tags: { $size: 2 } })
// Array with minimum size
db.users.find({ tags: { $exists: true, $ne: [] } })
// Array with maximum size
db.users.find({ $expr: { $lte: [{ $size: "$tags" }, 5] } })Nested Document Queries
Dot Notation
// Query nested field
db.users.find({ "profile.firstName": "John" })
// Query nested array
db.users.find({ "profile.addresses.city": "New York" })
// Query nested object
db.users.find({ "profile.contact.email": "john@example.com" })Nested Object Matching
// Match entire nested object
db.users.find({
profile: {
firstName: "John",
lastName: "Doe",
age: 30
}
})
// Match nested object with conditions
db.users.find({
"profile.age": { $gte: 25 },
"profile.city": "New York"
})Nested Array Queries
// Nested array element
db.users.find({ "profile.addresses.0.city": "New York" })
// Nested array with elemMatch
db.users.find({
"profile.addresses": {
$elemMatch: {
type: "home",
city: "New York"
}
}
})Projection Queries
Field Selection
// Include specific fields
db.users.find({}, { name: 1, email: 1, _id: 0 })
// Exclude specific fields
db.users.find({}, { password: 0, secretKey: 0 })
// Include nested fields
db.users.find({}, {
"profile.firstName": 1,
"profile.lastName": 1,
_id: 0
})
// Mixed inclusion/exclusion
db.users.find({}, {
name: 1,
email: 1,
password: 0,
_id: 0
})Conditional Projection
// Conditional field inclusion
db.users.find({}, {
name: 1,
email: 1,
age: { $cond: { if: { $gte: ["$age", 18] }, then: "$age", else: "Under 18" } },
_id: 0
})
// Computed fields
db.users.find({}, {
name: 1,
fullName: { $concat: ["$firstName", " ", "$lastName"] },
_id: 0
})Aggregation Queries
Basic Aggregation
// Simple aggregation
db.users.aggregate([
{ $match: { age: { $gte: 25 } } },
{ $group: { _id: "$city", count: { $sum: 1 } } },
{ $sort: { count: -1 } }
])
// Aggregation with multiple stages
db.users.aggregate([
{ $match: { status: "active" } },
{ $group: { _id: "$city", avgAge: { $avg: "$age" } } },
{ $sort: { avgAge: -1 } },
{ $limit: 5 }
])Aggregation Stages
// $match stage
{ $match: { age: { $gte: 25 } } }
// $group stage
{ $group: { _id: "$city", totalUsers: { $sum: 1 } } }
// $sort stage
{ $sort: { age: 1 } }
// $limit stage
{ $limit: 10 }
// $skip stage
{ $skip: 5 }
// $project stage
{ $project: { name: 1, age: 1, _id: 0 } }
// $lookup stage (join)
{
$lookup: {
from: "orders",
localField: "_id",
foreignField: "userId",
as: "orders"
}
}
// $unwind stage
{ $unwind: "$tags" }Advanced Query Techniques
Compound Queries
// Complex logical query
db.users.find({
$and: [
{ age: { $gte: 18 } },
{ status: "active" },
{
$or: [
{ city: "New York" },
{ city: "Los Angeles" }
]
},
{
$not: {
tags: { $in: ["spam", "bot"] }
}
}
]
})Performance Queries
// Covered query (index only)
db.users.find(
{ email: "john@example.com" },
{ _id: 0, email: 1 }
)
// Query with hint
db.users.find({ age: { $gte: 25 } }).hint({ age: 1 })
// Query with explain
db.users.find({ age: { $gte: 25 } }).explain("executionStats")Geospatial Queries
// Near query
db.users.find({
location: {
$near: {
$geometry: {
type: "Point",
coordinates: [-73.935242, 40.730610]
},
$maxDistance: 10000
}
}
})
// Within query
db.users.find({
location: {
$geoWithin: {
$centerSphere: [
[-73.935242, 40.730610], 0.01
]
}
}
})Time-based Queries
// Recent documents
db.users.find({
createdAt: { $gte: new Date(Date.now() - 24 * 60 * 60 * 1000) }
})
// Documents in date range
db.users.find({
createdAt: {
$gte: new Date("2023-01-01"),
$lt: new Date("2023-12-31")
}
})
// Documents by day of week
db.users.find({
$expr: {
$eq: [{ $dayOfWeek: "$createdAt" }, 1] // Monday
}
})Last updated