Difference between revisions of "FIND Tutorial"

Revision as of 12:57, 17 October 2018

Working with the `world` collection of countries

This tutorial introduces NoSQL using MongoDB. 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.

Show Germany

 Use find() to show the details of Germany.

Show Germany instead of France.

db.world.find({name:'France'});

db.world.find({name:'Germany'});

Eurasia

 You can use .pretty() to make the output more readable.

List all the countries in the continent of "Eurasia".

db.world.find({name:'Germany'}).pretty();

db.world.find({continent:"Eurasia"}).pretty();

Find an area

 You can test numbers as well as strings

Find the country with an area of exactly 43094.

db.world.find({gdp:3425956000000}).pretty();

db.world.find({area:43094}).pretty();

Using $gt

You can use $gt (greater than) and $lt (less than) to compare numbers and strings.

Show each country with a population of over 250000000
Sort the results alphabetically.

db.world.find(
  {area: {$gt: 9000000}},
  {name: 1, _id: 0}
).sort(
  {name: 1}
).pretty();

db.world.find({population:{$gt:250000000}},{name:1,_id:0}).sort({name: 1}).pretty();

After S

List the countries that come after "S" in the alphabet.

db.world.findOne();

db.world.find({name:{$gt:"S"}},{name:1,_id:0}).pretty();

Name and Capital

Find the name and capital cities for countries with a population of over 70 million.

db.world.findOne();

db.world.find({population:{$gt:70000000}},{name:1,capital:1,_id:0}).pretty();

Using $or

Find the countries that have a population that is over 200 million or less than 20,000.

db.world.find(
  {$or: [
    {name:'Germany'},
    {name:'France'}
  ]},
  {name: 1, population: 1, _id: 0}
);

db.world.find({$or:[{population:{$gt:200000000}},{population:{$lt:20000}}]},{name:1,population:1,_id:0})

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@@ Line 18: / Line 18: @@
 ==Eurasia==
 <div class="q" data-lang="mongo">
-   You can use .pretty() to make the output more readable.
+   You can use '''.pretty()''' to make the output more readable.
    <p class="strong">
      List all the countries in the continent of "Eurasia".
@@ Line 25: / Line 25: @@
    <pre class="ans"><nowiki>db.world.find({continent:"Eurasia"}).pretty();</nowiki></pre>
 </div>
 ==Find an area==
 <div class="q" data-lang="mongo">