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_______ groups documents by some specified expression and outputs to the next stage a document for each distinct grouping.(a) $setcon(b) $group(c) $match(d) None of the mentionedThis question was addressed to me in a national level competition.Origin of the question is SQL to Aggregation Mapping Chart in section Aggregation Concepts and Aggregation Mechanics of MongoDB

Answer» CORRECT answer is (b) $group

For EXPLANATION I WOULD say: $group works SIMILAR to group by clause in SQL.


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