Difference between revisions of "AGGREGATE world"
From NoSQLZoo
| Line 35: | Line 35: | ||
<div class="hint" title="How to calculate per capita GDP"> | <div class="hint" title="How to calculate per capita GDP"> | ||
per capita GDP is the GDP divided by the population GDP/population | per capita GDP is the GDP divided by the population GDP/population | ||
| + | </div> | ||
| + | <div class="hint" title="Using the aggregation framework"> | ||
| + | The aggregation framework is a data processing pipeline. There are many operators that you can use.<br/> | ||
| + | <code>$match</code> uses a query to limit or 'filter' what documents are to be used in the next stage of the pipeline.<br/> | ||
| + | <code>$project</code> is used to "shape" documents by adding or removing fields. It also allows you to compare fields with the syntax $<fieldname> | ||
| + | |||
</div> | </div> | ||
<pre class=def> | <pre class=def> | ||
| − | + | pp.pprint(list( | |
| + | db.world.aggregate([ | ||
| + | {"$match":{ | ||
| + | "population":{"$gte":250000000} | ||
| + | }}, | ||
| + | {"$project":{ | ||
| + | "_id":0, | ||
| + | "name":1, | ||
| + | "per capita GDP": {"$divide": ["$gdp","10"]} | ||
| + | }} | ||
| + | ]) | ||
| + | )) | ||
</pre> | </pre> | ||
<div class=ans> | <div class=ans> | ||
| − | + | pp.pprint(list( | |
| + | db.world.aggregate([ | ||
| + | {"$match":{ | ||
| + | "population":{"$gte":250000000} | ||
| + | }}, | ||
| + | {"$project":{ | ||
| + | "_id":0, | ||
| + | "name":1, | ||
| + | "per capita GDP": {"$divide": ["$gdp","$population"]} | ||
| + | }} | ||
| + | ]) | ||
| + | )) | ||
</div> | </div> | ||
</div> | </div> | ||
Revision as of 12:22, 16 July 2015
#ENCODING
import io
import sys
sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-16')
#MONGO
from pymongo import MongoClient
client = MongoClient()
client.progzoo.authenticate('scott','tiger')
db = client['progzoo']
#PRETTY
import pprint
pp = pprint.PrettyPrinter(indent=4)
Country Profile
For these questions you should use find() on the collection world
Show the name and population for the countries that have a population of at least 200 million.
pp.pprint(list(
db.world.find({},{"name":1,"_id":0})
))
pp.pprint(list(
db.world.find({"population":{"$gt":20000000}},{"name":1,"population":1,"_id":0})
))
Give the name and the per capita GDP for those countries with a population of at least 200 million.
per capita GDP is the GDP divided by the population GDP/population
The aggregation framework is a data processing pipeline. There are many operators that you can use.
$match uses a query to limit or 'filter' what documents are to be used in the next stage of the pipeline.
$project is used to "shape" documents by adding or removing fields. It also allows you to compare fields with the syntax $<fieldname>
pp.pprint(list(
db.world.aggregate([
{"$match":{
"population":{"$gte":250000000}
}},
{"$project":{
"_id":0,
"name":1,
"per capita GDP": {"$divide": ["$gdp","10"]}
}}
])
))
pp.pprint(list(
db.world.aggregate([
{"$match":{
"population":{"$gte":250000000}
}},
{"$project":{
"_id":0,
"name":1,
"per capita GDP": {"$divide": ["$gdp","$population"]}
}}
])
))