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.

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