Aggregation Operations

Question 1

Which operation is used to select specific documents?

Answer 1

{ $match: {find obj} }

Question 2

Which operation is used to sort documents?

Answer 2

{ $sort: {attr: 1/-1} }

Question 3

Which operation is used to add fields to documents?

Answer 3

{ $addFields: {fieldName: ‘$_attr’} }

Question 4

Which operation is used to specify the number of documents to return?

Answer 4

{$limit: val}

Question 5

Which operation is used to remove attributes from documents?

Answer 5

{ $project: {attr: 0} }

Question 6

Which operation is used to transform documents into the first normal form?

Answer 6

{ $unwind: ‘$attr of focus’ }

Question 7

Which operation is used to group documents when performing operations?

Answer 7

{ $group: {attrName: groupfunctions} }

Question 8

What are some commonly used group functions?

Answer 8

1. $sum/$avg/$min/$max: ‘$attr’ 2.$add/$multiply/$subtract/$divide: [‘$attr’, ‘attr’]