$push operator for adding to arrays in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the $push operator do in MongoDB?

The $push operator adds a specified value to an array field in a MongoDB document. If the array does not exist, it creates the array with the value.

intermediate

How do you add multiple values at once to an array using $push?

You use $push with the $each modifier to add multiple values to an array in one operation.

intermediate

Can $push be used to add elements in a sorted order?

Yes, by combining $push with $each and $sort, you can add elements and keep the array sorted.

beginner

What happens if you use $push on a field that is not an array?

MongoDB will return an error because $push expects the field to be an array or missing. It cannot push to a non-array field.

beginner

Write a simple MongoDB update query using $push to add the value 5 to the array field scores in documents where name is 'Alice'.

db.collection.updateOne({ name: 'Alice' }, { $push: { scores: 5 } })

What does the $push operator do in MongoDB?

A Creates a new collection

B Removes a value from an array

C Replaces an entire array

D Adds a value to an array field

$push adds a value to an existing array field or creates the array if it doesn't exist.

Which modifier allows $push to add multiple values at once?

A $all

B $each

C $multi

D $add

The $each modifier is used with $push to add multiple values to an array.

How can you keep an array sorted when adding new elements with $push?

A Use <code>$sort</code> with <code>$each</code>

B Use <code>$order</code>

C Use <code>$sort</code> alone

D MongoDB sorts arrays automatically

You combine $push with $each and $sort to add elements and keep the array sorted.

What error occurs if $push is used on a non-array field?

A Value is ignored

B Field is converted to an array automatically

C Operation fails with an error

D MongoDB deletes the field

$push requires the field to be an array or missing; otherwise, it throws an error.

Which MongoDB command adds the number 10 to the array values in documents where type is 'A'?

A db.collection.updateMany({ type: 'A' }, { $push: { values: 10 } })

B db.collection.insert({ type: 'A', values: 10 })

C db.collection.find({ type: 'A' }, { $push: { values: 10 } })

D db.collection.deleteMany({ type: 'A' }, { $push: { values: 10 } })

The updateMany with $push adds 10 to the values array for all documents where type is 'A'.

Explain how the $push operator works in MongoDB and give an example of adding multiple values to an array.

Think about updating documents with arrays and how to add one or many items.

Describe how to keep an array sorted when adding new elements using $push.

Consider how MongoDB can sort arrays during updates.