createIndex method in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the createIndex method do in MongoDB?

It creates an index on a collection to improve the speed of queries by organizing data for faster search.

beginner

How do you create a simple ascending index on the field name using createIndex?

Use db.collection.createIndex({ name: 1 }). The 1 means ascending order.

intermediate

What is the difference between ascending (1) and descending (-1) in createIndex?

Ascending (1) sorts the index from smallest to largest, descending (-1) sorts from largest to smallest. Both speed up queries but order matters for sorting.

intermediate

What option would you use with createIndex to ensure no duplicate values in the indexed field?

Use the option { unique: true } to prevent duplicate values in the indexed field.

intermediate

Can createIndex be used to create compound indexes? If yes, how?

Yes. You pass multiple fields in the object, like { field1: 1, field2: -1 } to create a compound index on both fields.

What is the main purpose of the createIndex method in MongoDB?

A To create a new collection

B To speed up query performance

C To backup the database

D To delete documents

Indexes help MongoDB find data faster, improving query speed.

Which of the following is the correct syntax to create an ascending index on the field age?

A db.collection.createIndex('age')

B db.collection.createIndex({ age: 'asc' })

C db.collection.createIndex({ age: 1 })

D db.collection.createIndex({ age: true })

The correct syntax uses 1 for ascending order.

How do you create a unique index on the field email?

A db.collection.createIndex({ email: 1 }, { unique: true })

B db.collection.createIndex({ email: 1 }, { unique: false })

C db.collection.createIndex({ email: 1 }, { duplicate: false })

D db.collection.createIndex({ email: 1 })

The option { unique: true } enforces uniqueness.

What does a compound index do?

A Indexes only one field

B Creates a backup of indexes

C Deletes multiple indexes

D Indexes multiple fields together

Compound indexes speed up queries involving multiple fields.

What does the value -1 mean in createIndex?

A Descending order

B Ascending order

C No order

D Unique index

-1 specifies descending order for the index.

Explain how to create a unique ascending index on the field 'username' in MongoDB.

Think about the syntax: db.collection.createIndex({ field: order }, { unique: true })

Describe the benefits of using the createIndex method in MongoDB.

Focus on performance and data integrity.