CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-frameworkpymongo
fear_matrix
fear_matrix

Reputation: 4960

$add two field values in mongodb

I am trying to solve an issue where I am trying to calculate the total cost of by doing a $add on Matches.ShippingCharge + Matches.PreownedPrice = Total.

I could have done it easily if Matches.ShippingCharge was only $ShippingCharge but since I am pulling data from 2 collection the approach seems to be different and I am not sure how to do it.

   gameresult = db.products.aggregate([
            {'$match': {'Platform':variable}},
            {'$lookup':{'from': 'vendorgames','localField': 'Product','foreignField': 'Product','as': 'Matches'}},
            {'$project': {'_id':0,'Product':'$Product','Price':'$Price','Matches.ShippingCharge':1,'Matches.PreownedPrice':1}}])

When I run the above query my result is so:

{u'Matches': [{u'ShippingCharge': 200, u'PreownedPrice': 2000}], u'Product': u'A Way Out', u'Price': u'2,499.00'}

What I want is the sum of Matches.ShippingCharge + Matches.PreownedPrice with $add function where the result will be the new total field. So my output should be like so:

{u'Matches': [{u'ShippingCharge': 200, u'PreownedPrice': 2000, u'Total': 2200 }], u'Product': u'A Way Out', u'Price': u'2,499.00'}

Upvotes: 1

Views: 2297

Answers (1)

Ashh
Ashh

Reputation: 46441

You need to use $add aggregation aggregation to add ShippingCharge and PreownedPrice fields

 gameresult = db.products.aggregate([
            {'$match': {'Platform':variable}},

            {'$lookup':{'from': 'vendorgames','localField': 'Product','foreignField': 'Product','as': 'Matches'}},

            {'$project': {'_id':0,
                'Product':'$Product',
                'Price':'$Price',
                'Matches.ShippingCharge':1,
                'Matches.PreownedPrice':1,
                'total': { $add: [ "$Matches.ShippingCharge", "$Matches.PreownedPrice" ] } }}
            ])

Upvotes: 2

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