Q1. How do you update a single document?
Use updateOne() to modify the first document matching the filter:
db.users.updateOne(
{ name: "John" },
{ $set: { age: 31, city: "Boston" } }
)
Q2. How do you update multiple documents?
Use updateMany() to modify all documents matching the filter:
db.users.updateMany(
{ age: { $lt: 18 } },
{ $set: { status: "minor" } }
)
Q3. What is the $inc operator?
$inc increments a numeric field by a specified value:
db.products.updateOne(
{ name: "Laptop" },
{ $inc: { stock: -1, sold: 1 } }
)
Q4. How do you update array fields?
Use array operators like $push, $pull, $addToSet:
db.users.updateOne(
{ name: "John" },
{ $push: { hobbies: "reading" } }
)
db.users.updateOne(
{ name: "John" },
{ $pull: { hobbies: "swimming" } }
)
Q5. What is upsert in update operations?
Upsert (update + insert) creates a new document if no document matches the filter. Set the upsert option to true:
db.users.updateOne(
{ email: "new@example.com" },
{ $set: { name: "New User" } },
{ upsert: true }
)