MongoDB\Collection::distinct()

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Definition

Parameters
Return Values
Errors/Exceptions
Behavior
Examples
See Also

Definition

MongoDB\Collection::distinct()

Finds the distinct values for a specified field across the collection.

function distinct(
    string $fieldName,
    array|object $filter = [],
    array $options = []
): mixed[]

Parameters

$fieldName : string

The field for which to return distinct values.

$filter : array|object

The filter criteria that specifies the documents from which to retrieve the distinct values.

$options : array

An array specifying the desired options.

Name	Type	Description
collation	array\|object	Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks. When specifying collation, the `locale` field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document. If the collation is unspecified but the collection has a default collation, the operation uses the collation specified for the collection. If no collation is specified for the collection or for the operation, MongoDB uses the simple binary comparison used in prior versions for string comparisons.
comment	mixed	Enables users to specify an arbitrary comment to help trace the operation through the database profiler, currentOp output, and logs. This option is available since MongoDB 4.4 and will result in an exception at execution time if specified for an older server version. New in version 1.13.
maxTimeMS	integer	The cumulative time limit in milliseconds for processing operations on the cursor. MongoDB aborts the operation at the earliest following interrupt point.
readConcern	MongoDB\Driver\ReadConcern	Read concern to use for the operation. Defaults to the collection's read concern. It is not possible to specify a read concern for individual operations as part of a transaction. Instead, set the `readConcern` option when starting the transaction.
readPreference	MongoDB\Driver\ReadPreference	Read preference to use for the operation. Defaults to the collection's read preference.
session	MongoDB\Driver\Session	Client session to associate with the operation. New in version 1.3.
typeMap	array	The type map to apply to cursors, which determines how BSON documents are converted to PHP values. Defaults to the collection's type map. New in version 1.5.

Return Values

An array of the distinct values.

Errors/Exceptions

MongoDB\Exception\UnexpectedValueException if the command response from the server was malformed.

MongoDB\Exception\UnsupportedException if options are used and not supported by the selected server (e.g. collation, readConcern, writeConcern).

MongoDB\Exception\InvalidArgumentException for errors related to the parsing of parameters or options.

MongoDB\Driver\Exception\RuntimeException for other errors at the extension level (e.g. connection errors).

Behavior

When evaluating query criteria, MongoDB compares types and values according to its own comparison rules for BSON types, which differs from PHP's comparison and type juggling rules. When matching a special BSON type the query criteria should use the respective BSON class in the extension (e.g. use MongoDB\BSON\ObjectId to match an ObjectId).

Examples

Return Distinct Values for a Field

The following example identifies the distinct values for the borough field in the restaurants collection in the test database.

<?php
$collection = (new MongoDB\Client)->test->restaurants;
$distinct = $collection->distinct('borough');
var_dump($distinct);

The output would then resemble:

array(6) {
  [0]=>
  string(5) "Bronx"
  [1]=>
  string(8) "Brooklyn"
  [2]=>
  string(9) "Manhattan"
  [3]=>
  string(7) "Missing"
  [4]=>
  string(6) "Queens"
  [5]=>
  string(13) "Staten Island"
}

Return Distinct Values Using a Filter

The following example identifies the distinct values for the cuisine field in the restaurants collection in the test database for documents where the borough is Queens:

<?php
$collection = (new MongoDB\Client)->test->restaurants;
$distinct = $collection->distinct('cuisine', ['borough' => 'Queens']);
var_dump($distinct);