Update README.md

Author: ruanbekker

README.md

@@ -131,3 +131,51 @@ MongoDB also has a count method:
 >>> transactions.find({'purchase_method': 'cash'}).count()
 2
 ```
+
+### Filters
+
+Find all the documents with purchase price > 120:
+
+```
+>>> response = transactions.find({'total_costs': {'$gt': 120}})
+>>> [doc for doc in response]
+[{u'account_id': u'sns_09121024', u'store_name': u'sportsmans', u'purchase_method': u'credit card', u'branch_name': u'tygervalley', u'products_purchased': [u'sportsdrink', u'sunglasses', u'sports illustrated'], u'_id': ObjectId('5cad18d4a5f3826f6f046d75'), u'total_costs': 129.84}, {u'account_id': u'gm_49121229', u'store_name': u'game', u'purchase_method': u'cash', u'branch_name': u'bellvile', u'products_purchased': [u'ps4 remote'], u'_id': ObjectId('5cad18d4a5f3826f6f046d77'), u'total_costs': 499.99}]
+```
+
+### Projections
+
+Select specific fields from the returned response:
+
+```
+>>> response = transactions.find({}, {'branch_name': 'tygervalley', 'purchase_method': 'credit card'})
+>>> [doc for doc in response]
+[{u'purchase_method': u'credit card', u'branch_name': u'tygervalley', u'_id': ObjectId('5cad16a5a5f3826f6f046d74')}, {u'purchase_method': u'credit card', u'branch_name': u'tygervalley', u'_id': ObjectId('5cad18d4a5f3826f6f046d75')}, {u'purchase_method': u'cash', u'branch_name': u'somerset west', u'_id': ObjectId('5cad18d4a5f3826f6f046d76')}, {u'purchase_method': u'cash', u'branch_name': u'bellvile', u'_id': ObjectId('5cad18d4a5f3826f6f046d77')}]
+```
+
+### Sorting Documents
+
+Sorting Documents in Descending Order:
+
+```
+>>> from pymongo import MongoClient, DESCENDING
+>>> response = transactions.find().sort('total_costs', DESCENDING)
+>>> ['Products: {}, Price: {}'.format(doc['products_purchased'], doc['total_costs']) for doc in response]
+["Products: [u'ps4 remote'], Price: 499.99", "Products: [u'sportsdrink', u'sunglasses', u'sports illustrated'], Price: 129.84", "Products: [u'cricket bat', u'cricket ball', u'sports hat'], Price: 109.2", "Products: [u'cheese burger', u'pepsi'], Price: 89.99"]
+```
+
+### Aggregations
+
+```
+>>> agr = [{'$group': {'_id': 1, 'all': { '$sum': '$total_costs' }}}]
+>> [a for a in transactions.aggregate(agr)]
+[{u'all': 829.02, u'_id': 1}]
+```
+
+or:
+
+```
+>>> agr = [{'$group': {'_id': 1, 'all': { '$sum': '$total_costs' }}}]
+>>> val = list(transactions.aggregate(agr))
+>>> val
+[{u'all': 829.02, u'_id': 1}]
+```