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A. No, it will throw an error.

B. Yes, it will only insert a document with an _id field (auto-generated).

C. Yes, it will only insert a document without any fields.

A. Yes

B. No

A. The Aggregation Framework will automatically reorder stages in a certain conditions (for optimization).

B. The query in a $match stage can not be entirely covered by an index.

A. db.collection.dropIndex()

B. db.collection.dropCollection()

C. db.collection.remove()

D. db.collection.drop()

A. It's good data modeling practice to directly map each table from the relational model (normalized data) to the collection.

B. To avoid having to join data in the application layer from different collections you can denormalize your data.

C. If one of your application's main queries is to retrieve related information from different collections, it is usually better to group that information into a single document.

A. db.companies.aggregate( [ { "$sortByCount": "$category_code" } ] )

B. ascending

C. descending

A. Internet Official Protocol Standards

B. Input/Output per Second

A. The earlier in the pipeline, the better. Not only because we will be using expression filters which reduce the number of documents to be processed, but also because we can use indexes.

B. It doesn't matter when we apply $match stage.

C. The later in the pipeline, the better.

A. db.movies.aggregate( { $group: { _id: '$rated', count: { $avg: 1 } } } )

B. db.movies.aggregate( { $group: { _id: '$rated', $count: { $sum: 1 } } } )

C. db.movies.aggregate( { $group: { _id: '$rated', count: { $sum: 1 } } } )

D. db.movies.aggregate( { $group: { _id: 'rated', count: { $sum: 1 } } } )

A. db.developers.updateOne( { _id: 1 }, { $set: { _id: 3, fname: 'Bob' } } )

B. db.developers.updateOne( { _id: 1 }, { $set: { fname: 'John' } } )

C. db.developers.updateOne( { _id: 1 }, { $unset: { _id: '' } } )

D. db.developers.updateOne( { _id: 1 }, { $set: { _id: 3 } } )

A. { _id: ObjectId("61af47c6e29861661d063714"), account_id: 1010, type: 'investment', limit: 1000000 }

B. { _id: ObjectId("61af47c6e29861661d067825"), account_id: 7355, type: 'commodity', limit: 500000 }

C. { _id: ObjectId("61af47c6e29861661d063357"), account_id: 1752, type: 'commodity', limit: 1000 }

D. { _id: ObjectId("61af47c6e29861661d063715"), account_id: 4336, type: 'derivatives', limit: 100000 }