Difference between revisions of "FIND Tutorial"
| Line 4: | Line 4: | ||
<div class='extra_space' style='width:1em; height:6em;'></div> | <div class='extra_space' style='width:1em; height:6em;'></div> | ||
<div class=q data-lang="mongo"> | <div class=q data-lang="mongo"> | ||
| − | Use <code>find()</code> to | + | Use <code>find()</code> to show the details of Germany |
<p class=strong>Show the 21st document in world</p> | <p class=strong>Show the 21st document in world</p> | ||
<pre class=def> | <pre class=def> | ||
| − | db.world.find() | + | db.world.find({name:'France'}) |
</pre> | </pre> | ||
<div class=ans> | <div class=ans> | ||
| − | db.world.find() | + | db.world.find({name:'Germany'}) |
</div> | </div> | ||
</div> | </div> | ||
Revision as of 15:17, 12 November 2015
Working with the world collection of countries
This tutorial introduces NoSQL using MonogDB and PyMongo under Python3.4. We will be using the find() command and comparison functions on the collection world which contains details of around 250 countries of the world:
FIND examples are available.
Use find() to show the details of Germany
Show the 21st document in world
db.world.find({name:'France'})
db.world.find({name:'Germany'})
List all the countries in the continent of Asia
db.world.find({},{"capital":1, "_id":0})
db.world.find({"continent":"Asia"}, {"_id":0, "name":1})
List the countries in Europe that start with the letter "S"
db.world.find({"name":{'$regex':"^S"},
"continent":"Europe"},{"name":1, "_id":0})
Find the capital cities for countries with a population of over 70 million
pp.pprint(list(db.world.find({"population":{"$gt":70000000}},{"capital":1,"_id":0})))
Find the countries that have a population of over 100 million or less than a million
pp.pprint(list(db.world.find({"$or":[{"population":{"$lt":1000000}},{"population":{"$gt":100000000}}]}, {"name":1, "_id":0})))
Find the names of countries beginning with "U" that are outside of Europe and North America
pp.pprint(list(db.world.find({"$and":[{"name":{'$regex':"^U"}},{"continent":{"$nin":["Europe", "North America"]}}]},{"name":1,"_id":0})))
Find the names of all countries that contain a white space
pp.pprint(list(db.world.find({"name":{"$regex":"^.*\s.*$"}},{"name":1,"_id":0})))
Which country out of China, Russia, and the United States has the largest population.
You might want to use Sort and limit to get the answer.
pp.pprint(list(db.world.find({"name":{"$in":["China", "Russia", "United States"]}}).sort("population",-1).limit(1)))
Use Sort to find the last document in world
Show the last document of world
pp.pprint(list(db.world.find().sort("$natural", -1))[0])
Show capital and population for the top 5 capital cities starting with the letter "M" that have a population of less than 3 million
pp.pprint(list(db.world.find({"$and":[{"capital":{"$regex":"^M"}},{"population":{"$lt":3000000}}]}, {"_id":0, "capital":1, "population":1}).sort("population",-1).limit(5)))
Show all the capitals for countries that start with the same letter as their continent
find({"$where": " boolean expression "})
pp.pprint(list(
db.world.find(
{"$where":"this.name[0]==this.continent[0]"},
{"_id":0, "capital":1})
))