Sum and Count: Difference between revisions
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..." |
No edit summary |
||
| Line 17: | Line 17: | ||
{{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 15:04, 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"))