MongoDB logical operators are used to combine multiple conditions in a query. They help us retrieve documents based on AND, OR, NOR, and NOT conditions.
In this lesson, we will learn how to use logical operators with practical examples from a student management database.
Logical operators allow us to combine or negate conditions when searching documents.
MongoDB provides four main logical operators:
| Operator | Meaning | Purpose |
|---|---|---|
$and |
Logical AND | All conditions must match. |
$or |
Logical OR | At least one condition must match. |
$nor |
Logical NOR | None of the conditions may match. |
$not |
Logical NOT | Negates a field query condition. |
Open MongoDB Shell (mongosh) and select a
database named school.
use school
Insert sample documents into a separate collection
named logical_students.
db.logical_students.insertMany([
{
name: "Rahul",
age: 18,
marks: 55,
course: "ADCA",
city: "Patna",
active: true
},
{
name: "Amit",
age: 20,
marks: 75,
course: "Python",
city: "Gaya",
active: true
},
{
name: "Priya",
age: 22,
marks: 90,
course: "Web Development",
city: "Patna",
active: false
},
{
name: "Neha",
age: 21,
marks: 65,
course: "Python",
city: "Aurangabad",
active: true
},
{
name: "Ravi",
age: 24,
marks: 40,
course: "ADCA",
city: "Gaya",
active: false
}
])Note: Run the insertion command only once to avoid duplicate sample documents.
The $and operator returns documents
only when all specified conditions are true.
db.collection.find({
$and: [
{ condition1 },
{ condition2 }
]
})db.logical_students.find({
$and: [
{ age: { $gt: 20 } },
{ marks: { $gt: 60 } }
]
})Result: Priya and Neha.
db.logical_students.find({
$and: [
{ course: "Python" },
{ active: true }
]
})Result: Amit and Neha.
db.logical_students.find({
$and: [
{ city: "Patna" },
{ marks: { $gt: 70 } }
]
})Result: Priya.
In MongoDB, you do not always need to write
$and explicitly.
When different fields are specified in the same filter, MongoDB applies AND logic automatically.
db.logical_students.find({
course: "Python",
active: true
})This is equivalent to:
db.logical_students.find({
$and: [
{ course: "Python" },
{ active: true }
]
})Both queries return active students enrolled in Python.
The $or operator returns documents
when at least one specified condition is true.
db.collection.find({
$or: [
{ condition1 },
{ condition2 }
]
})db.logical_students.find({
$or: [
{ city: "Patna" },
{ city: "Gaya" }
]
})Result: Rahul, Amit, Priya, and Ravi.
db.logical_students.find({
$or: [
{ course: "ADCA" },
{ course: "Python" }
]
})Result: Rahul, Amit, Neha, and Ravi.
db.logical_students.find({
$or: [
{ age: { $lt: 20 } },
{ marks: { $gt: 80 } }
]
})Result: Rahul and Priya.
The $nor operator returns documents
that do not satisfy any of the specified conditions.
db.collection.find({
$nor: [
{ condition1 },
{ condition2 }
]
})db.logical_students.find({
$nor: [
{ city: "Patna" },
{ city: "Gaya" }
]
})Result: Neha.
db.logical_students.find({
$nor: [
{ course: "ADCA" },
{ course: "Python" }
]
})Result: Priya.
db.logical_students.find({
$nor: [
{ age: { $lt: 20 } },
{ marks: { $gt: 80 } }
]
})Result: Amit, Neha, and Ravi.
The $not operator negates a field
query condition.
It is normally used with another operator,
such as $gt, $lt,
or $regex.
db.collection.find({
field: {
$not: { operator: value }
}
})db.logical_students.find({
age: {
$not: { $gt: 20 }
}
})Result: Rahul and Amit.
db.logical_students.find({
marks: {
$not: { $lt: 60 }
}
})Result: Amit, Priya, and Neha.
db.logical_students.find({
name: {
$not: { $regex: "^R" }
}
})Result: Amit, Priya, and Neha.
$not
operator may also match documents where the
specified field is missing.
Both operators can exclude values, but they are used differently.
db.logical_students.find({
age: { $ne: 20 }
})This finds documents where age is not equal to 20.
db.logical_students.find({
age: {
$not: { $gt: 20 }
}
})This finds documents where the condition age greater than 20 is not satisfied.
| $ne | $not |
|---|---|
| Compares against one value. | Negates another query condition. |
| Used for not-equal comparisons. | Used with operators such as $gt and $regex. |
| Example: age is not 20. | Example: age is not greater than 20. |
We can combine logical operators to create more advanced queries.
db.logical_students.find({
$and: [
{ active: true },
{
$or: [
{ city: "Patna" },
{ city: "Gaya" }
]
}
]
})Result: Rahul and Amit.
db.logical_students.find({
$and: [
{ age: { $gt: 20 } },
{
$or: [
{ course: "ADCA" },
{ course: "Python" }
]
}
]
})Result: Neha and Ravi.
db.logical_students.find({
active: true,
$or: [
{ marks: { $gt: 60 } },
{ age: { $lt: 20 } }
]
})Result: Rahul, Amit, and Neha.
Find active students whose marks are at least 60.
db.logical_students.find({
active: true,
marks: { $gte: 60 }
})Find employees working in IT or HR.
db.employees.find({
$or: [
{ department: "IT" },
{ department: "HR" }
]
})Find available products costing less than 5,000.
db.products.find({
available: true,
price: { $lt: 5000 }
})Find books that are available and belong to either Programming or Database categories.
db.books.find({
available: true,
$or: [
{ category: "Programming" },
{ category: "Database" }
]
})| Operator | Meaning | Example |
|---|---|---|
$and |
All conditions true | { $and: [{ age: 20 }, { active: true }] } |
$or |
At least one condition true | { $or: [{ age: 20 }, { age: 22 }] } |
$nor |
No condition true | { $nor: [{ age: 20 }, { age: 22 }] } |
$not |
Negates a field condition | { age: { $not: { $gt: 20 } } } |
Use the school database and the
logical_students collection to
complete the following tasks.
$or.$nor.$not.Challenge: Write a query to find students who are active and either have marks above 70 or are younger than 20.
1. Which operator requires all conditions to be true?
2. Which operator matches when at least one condition is true?
3. Which operator matches when none of the listed conditions is true?