Single field index in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a single field index in MongoDB?

A single field index is an index created on one field of a MongoDB collection to speed up queries that filter or sort by that field.

beginner

How do you create a single field index on the field 'age' in MongoDB?

Use the command: <br>db.collection.createIndex({ age: 1 })<br>Here, 1 means ascending order index.

beginner

What does the value 1 or -1 mean when creating a single field index?

1 means the index is created in ascending order, and -1 means descending order. Both speed up queries but may affect sort order.

beginner

Why use a single field index?

It helps MongoDB find documents faster when searching or sorting by that field, improving query performance.

intermediate

Can a single field index speed up queries that filter on multiple fields?

No, single field indexes only help queries filtering or sorting on that one field. For multiple fields, use compound indexes.

Which MongoDB command creates a single field index on 'name' in ascending order?

A db.collection.createIndex({ name: 1 })

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

C db.collection.createIndex({ name: true })

D db.collection.createIndex({ name: 'ascending' })

The correct syntax uses 1 for ascending order: db.collection.createIndex({ name: 1 })

What does the number -1 mean when creating a single field index?

A Index in ascending order

B Index in descending order

C Index disabled

D Index on multiple fields

-1 means the index is created in descending order.

Which of these is true about single field indexes?

A They speed up queries filtering on one field

B They speed up queries filtering on multiple fields

C They slow down queries

D They are only for sorting, not filtering

Single field indexes speed up queries filtering or sorting on that one field.

If you want to speed up queries filtering on two fields, what should you use?

A Text index

B Single field index

C No index

D Compound index

Compound indexes cover multiple fields and speed up queries filtering on those fields.

What happens if you create a single field index on a field that is rarely used in queries?

A It will slow down all queries

B It will always speed up queries

C It may not improve performance much

D It deletes documents

Indexes help only if queries use that field; otherwise, the index adds overhead without benefit.

Explain what a single field index is and how it helps MongoDB queries.

Think about how an index is like a shortcut to find data faster.

Describe the difference between using 1 and -1 when creating a single field index.

Consider how sorting can be from smallest to largest or largest to smallest.