Query Operators
Filtering data precisely is essential to working with MongoDB. Query operators let you go far beyond simple equality matches — comparing values, combining conditions, checking field existence, and querying inside arrays.
1. Comparison Operators
| Operator | Meaning | Example |
|---|---|---|
$eq | Equal to | { age: { $eq: 25 } } |
$ne | Not equal to | { status: { $ne: "inactive" } } |
$gt / $gte | Greater than / or equal | { price: { $gt: 500 } } |
$lt / $lte | Less than / or equal | { stock: { $lte: 10 } } |
$in | Matches any value in array | { city: { $in: ["Delhi", "Mumbai"] } } |
$nin | Matches none of the values | { city: { $nin: ["Pune"] } } |
2. Logical Operators
// AND (implicit)
db.products.find({ category: "Electronics", price: { $lt: 5000 } })
// Explicit $and
db.products.find({
$and: [ { price: { $gt: 100 } }, { price: { $lt: 1000 } } ]
})
// $or
db.products.find({
$or: [ { category: "Books" }, { category: "Stationery" } ]
})
// $nor
db.products.find({
$nor: [ { inStock: false }, { discontinued: true } ]
})3. Element Operators
// Field must exist
db.users.find({ phone: { $exists: true } })
// Field type check
db.users.find({ age: { $type: "int" } })4. Array Operators
| Operator | Purpose | Example |
|---|---|---|
$all | Array contains all specified values | { tags: { $all: ["node", "react"] } } |
$size | Array has exact length | { tags: { $size: 3 } } |
$elemMatch | At least one array element matches all conditions | { scores: { $elemMatch: { $gt: 80, $lt: 95 } } } |
db.orders.find({
items: { $elemMatch: { product: "Laptop", quantity: { $gte: 2 } } }
})
Pro Tip: Without
$elemMatch, MongoDB matches if any combination of array elements satisfies the conditions separately — not necessarily the same element. Use $elemMatch when conditions must apply to a single array item.
5. Combining Operators
db.products.find({
$and: [
{ category: { $in: ["Electronics", "Computers"] } },
{ price: { $gte: 1000, $lte: 50000 } },
{ $or: [ { brand: "Dell" }, { brand: "HP" } ] }
]
})6. Query Operators Checklist
- ✅ Master comparison operators — $gt, $lt, $in, $ne
- ✅ Combine conditions with $and, $or, $nor
- ✅ Check field existence and type with $exists, $type
- ✅ Query arrays precisely with $elemMatch and $all
Key Takeaway: Query operators are how you turn raw filtering into precise, expressive logic. Combine them thoughtfully, and always test against edge cases like empty arrays and missing fields.
Ready to master MongoDB?
Build real-world MongoDB-powered applications with hands-on projects, mentor-led sessions, and placement support.