Covered queries with indexes in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an index on the 'age' field.

MongoDB

db.users.createIndex([1]: 1})

Drag options to blanks, or click blank then click option'

Aemail

Bname

Cage

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a field not used in the query filter.

Using the wrong field name.

The index is created on the 'age' field to optimize queries filtering by age.

2fill in blank

medium

Complete the query to find users aged 30 using the index.

MongoDB

db.users.find([1]: 30})

Drag options to blanks, or click blank then click option'

Aage

Bemail

Cname

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Filtering by a non-indexed field.

Using a field name that does not exist.

The query filters users by the 'age' field, which is indexed for faster lookup.

3fill in blank

hard

Fix the error in the index creation by choosing the correct index type for a covered query.

MongoDB

db.users.createIndex([1]: 1})

Drag options to blanks, or click blank then click option'

Aaddress

Bname

Cemail

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using an unrelated field for the index.

Not including the fields needed for the covered query.

Covered queries require the index to include the fields used in the query and projection. Indexing 'age' supports this.

4fill in blank

hard

Fill both blanks to create a compound index on 'age' and 'name' for a covered query.

MongoDB

db.users.createIndex([1]: 1, [2]: 1})

Drag options to blanks, or click blank then click option'

Aage

Bemail

Cname

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing fields not used together in queries.

Creating single-field indexes instead of compound.

A compound index on 'age' and 'name' supports queries filtering and projecting these fields, enabling covered queries.

5fill in blank

hard

Fill all three blanks to write a covered query that uses the compound index on 'age' and 'name' and projects only 'name'.

MongoDB

db.users.find([1]: 25}, [2]: 1, [3]: 0})

Drag options to blanks, or click blank then click option'

Aage

Bname

Cemail

D_id

Attempts:

3 left

💡 Hint

Common Mistakes

Projecting fields not in the index.

Not excluding '_id' when needed for covered queries.

The query filters by 'age', projects 'name', and excludes '_id' to use the compound index for a covered query.