distinct¶

Definition¶

distinct¶

Finds the distinct values for a specified field across a single collection. distinct returns a document that contains an array of the distinct values. The return document also contains a subdocument with query statistics and the query plan.

When possible, the distinct command uses an index to find documents and return values.

The command takes the following form:

{ distinct: "<collection>", key: "<field>", query: <query> }

The command contains the following fields:

Field	Type	Description
`distinct`	string	The name of the collection to query for distinct values.
`key`	string	The field to collect distinct values from.
`query`	document	Optional. A query specification to limit the input documents in the distinct analysis.

Examples¶

Return an array of the distinct values of the field ord_dt from all documents in the orders collection:

db.runCommand ( { distinct: "orders", key: "ord_dt" } )

Return an array of the distinct values of the field sku in the subdocument item from all documents in the orders collection:

db.runCommand ( { distinct: "orders", key: "item.sku" } )

Return an array of the distinct values of the field ord_dt from the documents in the orders collection where the price is greater than 10:

db.runCommand ( { distinct: "orders",
                  key: "ord_dt",
                  query: { price: { $gt: 10 } }
                } )

注解

MongoDB also provides the shell wrapper method db.collection.distinct() for the distinct command. Additionally, many MongoDB drivers also provide a wrapper method. Refer to the specific driver documentation.

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