Difference between revisions of "Sum and Count"
From NoSQLZoo
(Created page with "<pre class=setup> #ENCODING import io import sys sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-16') #MONGO from pymongo import MongoClient client = MongoClien...") |
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{{TopTenTips}} | {{TopTenTips}} | ||
<div style="height:25em"> | <div style="height:25em"> | ||
| + | There are many ways to do this in MongoDB.<br/><br/> | ||
| + | <code>count()</code> is a cursor method that takes a query and returns a number equal to the amount of documents that matched the query.<br/> | ||
| + | <code>$sum</code> is an aggregation operator availible in the <code>$group</code> stage, that can be used to both sum values and count the number of documents.<br/> | ||
| + | mapReduce can produce a sum or a count during the results stage. | ||
| + | </div> | ||
| + | <div class=q data-lang="py3">.count() | ||
| + | <div class="def"> | ||
| + | print(db.world.count("continent":"Africa")) | ||
| + | </div> | ||
| + | </div> | ||
| + | <div class=q data-lang="py3">$sum | ||
| + | <div class="def"> | ||
| + | pp.pprint(list( | ||
| + | db.world.aggregate([ | ||
| + | {"$group":{ | ||
| + | "_id":"$continent", | ||
| + | "sum of population":{"$sum":"$population"}, | ||
| + | "count of countries":{"$sum":1} | ||
| + | }} | ||
| + | ]) | ||
| + | )) | ||
</div> | </div> | ||
| − | <div class=q data-lang="py3"> | + | </div> |
| + | |||
| + | <div class=q data-lang="py3">.count() | ||
<div class="def"> | <div class="def"> | ||
| + | print(db.world.count("continent":"Africa")) | ||
</div> | </div> | ||
</div> | </div> | ||
Revision as of 16:04, 27 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)
#CODE
from bson.code import Code
There are many ways to do this in MongoDB.
count() is a cursor method that takes a query and returns a number equal to the amount of documents that matched the query.
$sum is an aggregation operator availible in the $group stage, that can be used to both sum values and count the number of documents.
mapReduce can produce a sum or a count during the results stage.
.count()
print(db.world.count("continent":"Africa"))
$sum
pp.pprint(list(
db.world.aggregate([
{"$group":{
"_id":"$continent",
"sum of population":{"$sum":"$population"},
"count of countries":{"$sum":1}
}}
])
))
.count()
print(db.world.count("continent":"Africa"))