Projection for selecting fields in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is projection in MongoDB?

Projection is a way to select only specific fields from documents in a collection, so you get only the data you need.

beginner

How do you exclude a field using projection in MongoDB?

Set the field to 0 in the projection object to exclude it. For example, { fieldName: 0 } excludes that field.

beginner

How do you include multiple fields in a MongoDB projection?

Set each field you want to include to 1 in the projection object. For example, { name: 1, age: 1 } includes only name and age fields.

intermediate

Can you mix including and excluding fields in MongoDB projection?

No, except for the _id field. You either include fields (set to 1) or exclude fields (set to 0), but not both at the same time.

beginner

What is the default behavior of MongoDB if no projection is specified?

MongoDB returns the entire document with all fields when no projection is specified.

In MongoDB, how do you select only the 'name' and 'age' fields from documents?

A { name: true, age: true }

B { name: 0, age: 0 }

C { name: 1, age: 1 }

D { name: 'include', age: 'include' }

Setting fields to 1 in the projection includes them in the result.

What happens if you set a field to 0 in a MongoDB projection?

A The field is excluded from the result

B The field is included in the result

C The query fails

D The field is renamed

Setting a field to 0 excludes it from the returned documents.

Can you exclude the '_id' field in a MongoDB projection?

A Yes, by setting '_id' to 0

B No, '_id' is always included

C Only if you include other fields

D Only in aggregation pipelines

You can exclude '_id' by setting it to 0 in the projection.

Which of the following is NOT allowed in MongoDB projection?

A Including multiple fields

B Mixing inclusion and exclusion of fields except '_id'

C Excluding multiple fields

D Excluding '_id' field

You cannot mix including and excluding fields in the same projection except for '_id'.

If you do not specify a projection in a MongoDB find query, what is returned?

A An error occurs

B Only the '_id' field

C No fields are returned

D The entire document with all fields

By default, MongoDB returns the full document if no projection is specified.

Explain how to use projection in MongoDB to include only certain fields in your query results.

Think about how you tell MongoDB which fields to show.

Describe the rules and limitations when mixing inclusion and exclusion in MongoDB projections.

Remember the special case with the _id field.