Combining logical and comparison operators in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the $and operator do in MongoDB queries?

The $and operator combines multiple conditions and returns documents that satisfy all of them.

beginner

How do you use comparison operators like $gt and $lt in MongoDB?

Comparison operators like $gt (greater than) and $lt (less than) are used inside query objects to filter documents based on field values.

intermediate

Explain how to combine $or with comparison operators in a MongoDB query.

You use $or to specify multiple alternative conditions. Each condition can use comparison operators. The query returns documents matching any one of the conditions.

beginner

What is the difference between $and and $or in MongoDB queries?

$and requires all conditions to be true for a document to match, while $or requires at least one condition to be true.

beginner

How would you write a MongoDB query to find documents where age is greater than 25 and status is 'active'?

Use { $and: [ { age: { $gt: 25 } }, { status: 'active' } ] }. This finds documents where both conditions are true.

Which operator in MongoDB returns documents that satisfy all given conditions?

A $nor

B $or

C $not

D $and

The $and operator requires all conditions to be true for a document to match.

How do you check if a field 'score' is less than 50 in MongoDB?

A { score: { $eq: 50 } }

B { score: { $lt: 50 } }

C { score: 50 }

D { score: { $gt: 50 } }

The $lt operator means 'less than', so { score: { $lt: 50 } } finds documents with score less than 50.

What does the following query do? { $or: [ { age: { $gt: 30 } }, { status: 'active' } ] }

A Finds documents where age is greater than 30 and status is 'active'

B Finds documents where age is less than 30 or status is not 'active'

C Finds documents where age is greater than 30 or status is 'active'

D Finds documents where age equals 30 or status equals 'active'

The $or operator returns documents matching any one of the conditions.

Which operator would you use to combine conditions that all must be true?

A $and

B $or

C $nor

D $exists

$and combines conditions that all must be true.

How do you write a query to find documents where 'price' is between 10 and 20 inclusive?

A { price: { $gte: 10, $lte: 20 } }

B { price: { $lt: 10, $gt: 20 } }

C { price: { $gt: 10, $lt: 20 } }

D { price: { $eq: 10, $eq: 20 } }

$gte means greater than or equal, $lte means less than or equal, so this finds prices between 10 and 20 inclusive.

Describe how to combine logical operators with comparison operators in a MongoDB query.

Think about how you can ask for multiple conditions at once.

Explain the difference between $and and $or operators in MongoDB with examples.

Think about 'all' versus 'any' conditions.