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$multiply (aggregation)
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Definition
$multiplyMultiplies numbers together and returns the result. Pass the arguments to
$multiplyin an array.The
$multiplyexpression has the following syntax:{ $multiply: [ <expression1>, <expression2>, ... ] } The arguments can be any valid expression as long as they resolve to numbers. For more information on expressions, see Expressions.
Example
Consider a sales collection with the following documents:
{ "_id" : 1, "item" : "abc", "price" : 10, "quantity": 2, date: ISODate("2014-03-01T08:00:00Z") } { "_id" : 2, "item" : "jkl", "price" : 20, "quantity": 1, date: ISODate("2014-03-01T09:00:00Z") } { "_id" : 3, "item" : "xyz", "price" : 5, "quantity": 10, date: ISODate("2014-03-15T09:00:00Z") }
The following aggregation uses the $multiply expression
in the $project pipeline to multiply the price and the
quantity fields:
db.sales.aggregate( [ { $project: { date: 1, item: 1, total: { $multiply: [ "$price", "$quantity" ] } } } ] )
The operation returns the following results:
{ "_id" : 1, "item" : "abc", "date" : ISODate("2014-03-01T08:00:00Z"), "total" : 20 } { "_id" : 2, "item" : "jkl", "date" : ISODate("2014-03-01T09:00:00Z"), "total" : 20 } { "_id" : 3, "item" : "xyz", "date" : ISODate("2014-03-15T09:00:00Z"), "total" : 50 }