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Aggregation Commands

注解

For details on specific commands, including syntax and examples, click on the specific command to go to its reference page.

Name Description
aggregate Performs aggregation tasks such as group using the aggregation framework.
count Counts the number of documents in a collection.
distinct Displays the distinct values found for a specified key in a collection.
group Deprecated. Groups documents in a collection by the specified key and performs simple aggregation.
mapReduce Performs map-reduce aggregation for large data sets.

For a detailed comparison of the different approaches, see Aggregation Commands Comparison.