Query and Update Operators

MongoDB operators let you express conditions and updates.

They usually start with $.

Query operators

Greater than:

db.products.find({ price: { $gt: 100 } })

In list:

db.products.find({ category: { $in: ['books', 'electronics'] } })

Or condition:

db.users.find({
  $or: [{ role: 'admin' }, { verified: true }],
})

Update operators

Set a field:

db.users.updateOne(
  { email: 'asha@example.com' },
  { $set: { active: true } },
)

Increment:

db.posts.updateOne(
  { _id: postId },
  { $inc: { views: 1 } },
)

Push into array:

db.posts.updateOne(
  { _id: postId },
  { $push: { tags: 'mongodb' } },
)

Common operators

Operator	Use
`$set`	set field value
`$inc`	increment number
`$push`	add to array
`$in`	match any value in list
`$gt` / `$lt`	greater than / less than
`$or`	match any condition

Common mistake

Be careful with update without operators.

Depending on API usage, you may replace more of the document than expected.

Use $set when updating specific fields.

Interview answer

MongoDB query operators define matching conditions, such as $gt, $in, and $or. Update operators modify documents, such as $set, $inc, and $push. Operators make queries and updates expressive without manually reading and rewriting whole documents.