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- $sum (aggregation)
$sum (aggregation)¶
-
$sum
¶ Returns the sum of all the values for a specified field in the grouped documents, as in the second use above.
Alternately, if you specify a value as an argument,
$sum
will increment this field by the specified value for every document in the grouping. Typically, as in the first use above, specify a value of1
in order to count members of the group.