Why logical operators matter in MongoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find documents where age is greater than 25.

MongoDB

db.users.find({ age: { [1]: 25 } })

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

A$lt

B$gt

C$eq

D$ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt will find ages less than 25, which is wrong here.

Using $eq looks for exactly 25, not greater than 25.

The $gt operator means 'greater than'. It finds documents where the age is more than 25.

2fill in blank

medium

Complete the code to find documents where status is either 'A' or 'B'.

MongoDB

db.orders.find({ [1]: [ { status: 'A' }, { status: 'B' } ] })

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

A$or

B$not

C$and

D$nor

Attempts:

3 left

💡 Hint

Common Mistakes

Using $and requires both conditions to be true, which is too strict here.

Using $not negates a condition, which is not what we want.

The $or operator finds documents matching any of the conditions inside the array.

3fill in blank

hard

Fix the error in the query to find documents where age is greater than 20 and less than 30.

MongoDB

db.people.find({ [1]: [ { age: { $gt: 20 } }, { age: { $lt: 30 } } ] })

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

A$not

B$or

C$nor

D$and

Attempts:

3 left

💡 Hint

Common Mistakes

Using $or would find ages greater than 20 or less than 30, which is too broad.

Using $not or $nor changes the meaning to exclude conditions.

The $and operator ensures both conditions are true: age greater than 20 and less than 30.

4fill in blank

hard

Fill both blanks to find documents where score is greater than 80 and status is 'active'.

MongoDB

db.results.find({ [1]: [ { score: { $gt: 80 } }, { status: [2] } ] })

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

A$and

B'active'

C'inactive'

D$or

Attempts:

3 left

💡 Hint

Common Mistakes

Using $or would allow either condition, not both.

Using 'inactive' for status would find wrong documents.

Use $and to combine conditions and the string 'active' for the status value.

5fill in blank

hard

Fill all three blanks to find documents where age is between 18 and 25 inclusive, and status is not 'inactive'.

MongoDB

db.users.find({ [1]: [ { age: { [2]: 18 } }, { age: { [3]: 25 } }, { status: { $ne: 'inactive' } } ] })

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

A$and

B$gte

C$lte

D$or

Attempts:

3 left

💡 Hint

Common Mistakes

Using $or would allow any condition, not all.

Using $gt or $lt excludes the boundary values.

Use $and to combine conditions, $gte for 'greater than or equal to' 18, and $lte for 'less than or equal to' 25.