$min and $max accumulators in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the $min accumulator do in MongoDB aggregation?

The $min accumulator finds the smallest value for a specified field across grouped documents.

beginner

What is the purpose of the $max accumulator in MongoDB?

The $max accumulator returns the largest value for a specified field from grouped documents.

intermediate

How do $min and $max behave when used in a $group stage?

They compute the minimum and maximum values respectively for each group of documents defined by the _id field in the $group stage.

intermediate

Can $min and $max be used on fields with different data types?

They work best on comparable data types like numbers or dates. Mixing incompatible types can lead to unexpected results or errors.

beginner

Example: How to find the minimum and maximum price of products in each category using MongoDB aggregation?

Use $group with _id as category, and $min: "$price" and $max: "$price" to get min and max prices per category.

What does the $min accumulator return in a MongoDB aggregation?

A The smallest value of a field in grouped documents

B The largest value of a field in grouped documents

C The average value of a field

D The total count of documents

$min finds the smallest value for a specified field within each group.

Which accumulator would you use to find the highest score in a group of documents?

A <code>$max</code>

B <code>$min</code>

C <code>$avg</code>

D <code>$sum</code>

$max returns the largest value in the group.

In which aggregation stage are $min and $max typically used?

A <code>$sort</code>

B <code>$project</code>

C <code>$match</code>

D <code>$group</code>

$min and $max are used in $group to aggregate values per group.

What happens if you use $min on a field with mixed data types?

A It always returns the smallest number

B It may return unexpected results or errors

C It converts all values to strings

D It ignores non-numeric values

Using $min on mixed types can cause errors or unexpected results because values are not comparable.

How do you specify the field to find the minimum value of in $min?

A Use the field name in an array

B Use the field name as a string without $

C Use the field name prefixed with $ like "$fieldName"

D Use the field name in a nested object

You specify the field with a $ prefix, for example "$price".

Explain how $min and $max accumulators work in MongoDB aggregation.

Think about grouping documents and finding extreme values.

Describe a real-life example where you would use $min and $max in a database query.

Consider a store with products or a class with student scores.