Hướng dẫn multiply mongodb

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{ $multiply: [ , , ... ] }

{ "_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"] }

db.sales.aggregate[
   [
     { $project: { date: 1, item: 1, total: { $multiply: [ "$price", "$quantity" ] } } }
   ]
]

{ "_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 }

• Reference >
• Operators >
• Aggregation Pipeline Operators >
• $multiply [aggregation]

Definition¶

Multiplies numbers together and returns the result. Pass the arguments to $multiply in an array.

The $multiply expression has the following syntax:

{ $multiply: [ , , ... ] }

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 }