$multiply (aggregation)
Definition
$multiply
- Multiplies numbers together and returns the result. Pass thearguments to
$multiply
in an array.
The $multiply
expression has the following syntax:
- { $multiply: [ <expression1>, <expression2>, ... ] }
The arguments can be any valid expression as long as they resolve to numbers. Formore 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
expressionin the $project
pipeline to multiply the price
and thequantity
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 }