Difference between revisions of "Returning documents"

Latest revision as of 00:13, 9 April 2018

Top Tips

Return all documents

db.world.find()
db.world.aggregate([{"$match":{}}])

Returning the first document

db.world.findOne()
db.world.find()[0]
db.world.find().limit(1)
db.world.aggregate([{"$limit":1}])

Returning the nth document

let n = 50;
db.world.find()[n-1]
db.world.find().skip(n-1).limit(1)
db.world.aggregate([{"$skip":n-1},{"$limit":1}])

Returning the last document

db.world.find()[db.world.count()-1]
db.world.find().skip(db.world.count()-1).limit(1)
db.world.aggregate([{"$skip":db.world.count()-1},{"$limit":1}])

@@ Line 1: / Line 1: @@
-<pre class=setup>
-#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
-</pre>
 {{TopTenTips}}
 <div style='height:25em;'>
 </div>
-<div class=q data-lang="py3">MapReduce
+<div class="q" data-lang="mongo">Return all documents
-<pre class=def>
+<pre class="def">
-pp.pprint(db.world.find_one())
+db.world.find()
-pp.pprint(db.world.find()[1])
+db.world.aggregate([{"$match":{}}])
-pp.pprint(db.world.find().limit(1))
+</pre>
-pp.pprint(db.world.aggregate([{"$limit":1}])
+</div>
+<div class="q" data-lang="mongo">Returning the first document
+<pre class="def">
+db.world.findOne()
+db.world.find()[0]
+db.world.find().limit(1)
+db.world.aggregate([{"$limit":1}])
+</pre>
+</div>
+<div class="q" data-lang="mongo">Returning the '''n'''th document
+<pre class="def">
+let n = 50;
+db.world.find()[n-1]
+db.world.find().skip(n-1).limit(1)
+db.world.aggregate([{"$skip":n-1},{"$limit":1}])
+</pre>
+</div>
+<div class="q" data-lang="mongo">Returning the last document
+<pre class="def">
+db.world.find()[db.world.count()-1]
+db.world.find().skip(db.world.count()-1).limit(1)
+db.world.aggregate([{"$skip":db.world.count()-1},{"$limit":1}])
 </pre>
 </div>