#REDIRECT [[NoSQL Zoo]]

NoSQL Zoo

2025-03-29T18:35:16Z

Andr3w: Andr3w moved page Main Page to NoSQL Zoo

2021-03-31T22:53:37Z

Andr3w: /* Messing with continent names 4 */

==Country Profile==
For these questions you should use <code>aggregate([])</code> on the collection <code>world</code>

You may find these [[AGGREGATE examples]] useful.
<div class='extra_space' style='width:1em; height:6em;'></div>
==$group on continent==
<div class="q" data-lang="mongo">
The aggregate method allows a <code>$group</code> - you must specify the <code>_id</code> and you can use aggregating functions such as <code>$sum</code> <code>$min</code> <code>$max</code> <code>$push</code>

The sample code shows the total population of each continent.
<div class='imper'>Show the number of countries in each continent.</div>
<pre class="def"><nowiki>
db.world.aggregate({
$group: {
_id: '$continent',
res: {
$sum: '$population'
}
}
});</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate({
$group: {
_id: '$continent',
res: {
$sum: 1
}
}
});
</nowiki></pre>
</div>

==Per Capita GDP==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>per capita GDP</code> for those countries with a <code>population</code> of at least 200 million.
<div class="hint" title="How to calculate per capita GDP">
per capita GDP is the GDP divided by the population.
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
population: {$gte: 250000000}
}},
{$project: {
_id: 0,
name: 1,
"per capita GDP": {$divide: ['$gdp', 1000000]}
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"population":{"$gte":200000000}}},{"$project":{"_id":0,"name":1,"per capita GDP": {"$divide": ["$gdp","$population"]}}}]);</nowiki></pre>
</div>

==Population Density in South America==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>population density</code> of all countries in South America.
<div class="hint" title="How to calculate population density">
population density is the population divided by the area
</div>
<div class="hint" title="Division by 0 error?">
Use a <code>$match</code>. <code>{"area":{"$ne":0}}</code>
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {continent: 'Asia'}},
{$project: {
_id: 0,
name: 1,
density: {$divide: ["$population", "$area"]}
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$match:{continent:'South America'}},{$project:{_id:0,name:1,density:{$divide:["$population","$area"]}}}]);</nowiki></pre>
</div>
==Population Density for "V"==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>population density</code> of all countries with name after V in the alphabet.
<p>Note that because Vatican City (with area 0) is in Europe you will get a divide by zero error unless you filter first.
</p>
<div class="hint" title="Division by 0 error?">
Use a <code>$match</code>.
<pre>
{
$match: {
area: {
"$ne": 0
}
}
}
</pre>
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {name: {$gt: 'V'}}},
{$project: {
_id: 0,
name: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$match:{name:{$gt:'V'}}},{$match:{area:{"$ne":0}}},{$project:{_id:0,name:1,density:{$divide:["$population","$area"]}}}]);</nowiki></pre>
</div>
==Population in millions==
<div class="q" data-lang="mongo">
Show the <code>name</code> and <code>population</code> in millions for the countries of the continent <b>South America</b>. Divide the population by 1000000 to get population in millions.
<pre class="def"><nowiki>
db.world.aggregate([
{$match:{

}},
{$project:{
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"continent":{"$eq":"South America"}}},{"$project":{"_id":0,"name":1,"population":{"$divide":["$population",1000000]}}}]);</nowiki></pre>
</div>

==Population density==
<div class="q" data-lang="mongo">
Show the <code>name</code> and <code>population density</code> for <b>France</b>, <b>Germany</b>, and <b>Italy</b>
<pre class="def"><nowiki>
db.world.aggregate([
{$match:{
name: {$in: ['United Kingdom', 'United States', 'Brazil']},
population: {$ne: null},
area: {$ne: 0}
}},
{$project:{
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"name":{"$in":['France','Germany','Italy']},"population":{"$ne":null},"area":{"$ne":0}}},{"$project":{"_id":0,"name":1,"population density":{"$divide":["$population","$area"]}}}]);</nowiki></pre>
</div>
==Continents by area==
<div class="q" data-lang="mongo">
Order the <code>continents</code> by <code>area</code> from most to least.
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: "$name",
area: {$max: "$area"}
}},
{$sort: {
area: -1
}},
{$project: {
_id: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$group":{"_id":"$continent","area":{"$sum":"$area"}}},{"$sort":{"area":-1}},{"$project":{"_id":1,"area":1}}]);</nowiki></pre>
</div>

==Big Continents==
<div class="q" data-lang="mongo">
Show the only two continents with total area greater than 25000000 and then sort from largest to smallest.
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
continent: "North America"
}},
{$project: {
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$group:{_id:"$continent",area:{$sum:"$area"}}},{$sort:{area:-1}},{$match:{area:{$gt:25000000}}}]);</nowiki></pre>
</div>
==First and last country by continent==
<div class="q" data-lang="mongo">
For each continent show the first and last country alphabetically like this:
<syntaxhighlight lang="JavaScript>
{ "_id" : "Africa", "from" : "Algeria", "to" : "Zimbabwe" }
{ "_id" : "Asia", "from" : "Afghanistan", "to" : "Yemen" }
{ "_id" : "Caribbean", "from" : "Antigua and Barbuda", "to" : "Trinidad and Tobago" }
{ "_id" : "Eurasia", "from" : "Armenia", "to" : "Russia" }
{ "_id" : "Europe", "from" : "Albania", "to" : "Vatican City" }
{ "_id" : "North America", "from" : "Belize", "to" : "United States" }
{ "_id" : "Oceania", "from" : "Australia", "to" : "Vanuatu" }
{ "_id" : "South America", "from" : "Argentina", "to" : "Venezuela" }
</syntaxhighlight>
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: "$continent"
}},
{$sort: {
_id: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$sort:{name:1}},{$group:{_id:'$continent',from:{$first:'$name'},to:{$last:'$name'}},},{$sort:{_id:1}}])</nowiki></pre>
</div>

==Countries beginning with...==
<div class="q" data-lang="mongo">
Group countries according to the first letter of the name. As shown.
Only give "U" through to "Z".

You will need to use the '''$substr''' function and the '''$push''' aggregate function.
<syntaxhighlight lang="JavaScript">
{ "_id" : "U", "list" : [ "Uganda", "Ukraine", "United Arab Emirates", "United Kingdom", "United States", "Uruguay", "Uzbekistan" ] }
{ "_id" : "V", "list" : [ "Vanuatu", "Vatican City", "Venezuela", "Vietnam" ] }
{ "_id" : "Y", "list" : [ "Yemen" ] }
{ "_id" : "Z", "list" : [ "Zambia", "Zimbabwe" ] }
</syntaxhighlight>
<pre class="def"><nowiki>
db.world.aggregate([
{$project: {
_id: '$name',
startsWith: {$substr: ['$name', 0, 1]}
}},
{$match: {
_id: {$gte: 'U'}
}},
{$sort: {_id: 1}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$group:{_id:{$substr:['$name',0,1]},list:{$push:'$name'}}},{$match:{_id:{$gte:'U'}}},{$sort:{_id:1}}]);</nowiki></pre>
</div>

==Harder Questions==
==Messing with continent names==
<div class="q" data-lang="mongo">
Combine <b>North America</b> and <b>South America</b> to <b>America</b>, and then list the continents by area. Biggest first.
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: {
$cond: [
{$eq: ["$continent", "North America"]},
"America",
{$cond: [
{$eq: ["$continent", "Asia"]},
"The East",
"$continent"
]}
]
},
area: {$sum: "$area"}
}},
{$sort: {area: -1}},
{$project: {
_id: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$group":{"_id":{"$cond":[{"$eq":["$continent","South America"]},"America",{"$cond":[{"$eq":["$continent","North America"]},"America","$continent"]}]},"area":{"$sum":"$area"}}},{"$sort":{"area":-1}},{"$project":{"_id":1,"area":1}}]); </nowiki></pre>
</div>

==Country populations by order of magnitude==
<div class="q" data-lang="mongo">
Show the number of countries in each order.

For example UK has a population of 64,105,700 so it belongs in the 10,000,000 bucket.

You will need the functions $floor, $log10 and $pow

<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
name: {$regex: "^N"}
}},
{$project: {
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([
{$project: {name:1,l10:{$pow:[10,{$floor:{$log10:"$population"}}]}}},
{$group:{_id:"$l10",c:{$sum:1}}},
{$sort:{_id:1}}
]);
</nowiki></pre>
</div>

AGGREGATE Tutorial

2021-03-31T22:53:21Z

Andr3w: /* Messing with continent names 3 */

2020-12-11T19:24:52Z

Andr3w: /* Per Capita GDP */

==Country Profile==
For these questions you should use <code>aggregate([])</code> on the collection <code>world</code>

You may find these [[AGGREGATE examples]] useful.
<div class='extra_space' style='width:1em; height:6em;'></div>
==$group on continent=
<div class="q" data-lang="mongo">
The aggregate method allows a <code>$group/code> - you must specify the <code>_id</code> and you can use aggregating functions such as $sum $min $max $push
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
population: {$gte: 250000000}
}},
{$project: {
_id: 0,
name: 1,
"per capita GDP": {$divide: ['$gdp', 1000000]}
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate({
$group: {
_id: 'world',
res: {
$sum: 1
}
}
});
</nowiki></pre>

</div>

==Per Capita GDP==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>per capita GDP</code> for those countries with a <code>population</code> of at least 200 million.
<div class="hint" title="How to calculate per capita GDP">
per capita GDP is the GDP divided by the population.
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
population: {$gte: 250000000}
}},
{$project: {
_id: 0,
name: 1,
"per capita GDP": {$divide: ['$gdp', 1000000]}
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"population":{"$gte":200000000}}},{"$project":{"_id":0,"name":1,"per capita GDP": {"$divide": ["$gdp","$population"]}}}]);</nowiki></pre>
</div>

==Population Density in South America==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>population density</code> of all countries in South America.
<div class="hint" title="How to calculate population density">
population density is the population divided by the area
</div>
<div class="hint" title="Division by 0 error?">
Use a <code>$match</code>. <code>{"area":{"$ne":0}}</code>
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {continent: 'Asia'}},
{$project: {
_id: 0,
name: 1,
density: {$divide: ["$population", "$area"]}
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$match:{continent:'South America'}},{$project:{_id:0,name:1,density:{$divide:["$population","$area"]}}}]);</nowiki></pre>
</div>
==Population Density for "V"==
<div class="q" data-lang="mongo">
Give the <code>name</code> and the <code>population density</code> of all countries with name after V in the alphabet.
<p>Note that because Vatican City (with area 0) is in Europe you will get a divide by zero error unless you filter first.
</p>
<div class="hint" title="Division by 0 error?">
Use a <code>$match</code>.
<pre>
{
$match: {
area: {
"$ne": 0
}
}
}
</pre>
</div>
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {name: {$gt: 'V'}}},
{$project: {
_id: 0,
name: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$match:{name:{$gt:'V'}}},{$match:{area:{"$ne":0}}},{$project:{_id:0,name:1,density:{$divide:["$population","$area"]}}}]);</nowiki></pre>
</div>
==Population in millions==
<div class="q" data-lang="mongo">
Show the <code>name</code> and <code>population</code> in millions for the countries of the continent <b>South America</b>. Divide the population by 1000000 to get population in millions.
<pre class="def"><nowiki>
db.world.aggregate([
{$match:{

}},
{$project:{
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"continent":{"$eq":"South America"}}},{"$project":{"_id":0,"name":1,"population":{"$divide":["$population",1000000]}}}]);</nowiki></pre>
</div>

==Population density==
<div class="q" data-lang="mongo">
Show the <code>name</code> and <code>population density</code> for <b>France</b>, <b>Germany</b>, and <b>Italy</b>
<pre class="def"><nowiki>
db.world.aggregate([
{$match:{
name: {$in: ['United Kingdom', 'United States', 'Brazil']},
population: {$ne: null},
area: {$ne: 0}
}},
{$project:{
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"name":{"$in":['France','Germany','Italy']},"population":{"$ne":null},"area":{"$ne":0}}},{"$project":{"_id":0,"name":1,"population density":{"$divide":["$population","$area"]}}}]);</nowiki></pre>
</div>
==Continents by area==
<div class="q" data-lang="mongo">
Order the <code>continents</code> by <code>area</code> from most to least.
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: "$name",
area: {$max: "$area"}
}},
{$sort: {
area: -1
}},
{$project: {
_id: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$group":{"_id":"$continent","area":{"$sum":"$area"}}},{"$sort":{"area":-1}},{"$project":{"_id":1,"area":1}}]);</nowiki></pre>
</div>

==Big Continents==
<div class="q" data-lang="mongo">
Show the only two continents with total area greater than 25000000 and then sort from largest to smallest.
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
continent: "North America"
}},
{$project: {
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$group:{_id:"$continent",area:{$sum:"$area"}}},{$sort:{area:-1}},{$match:{area:{$gt:25000000}}}]);</nowiki></pre>
</div>
==First and last country by continent==
<div class="q" data-lang="mongo">
For each continent show the first and last country alphabetically like this:
<syntaxhighlight lang="JavaScript>
{ "_id" : "Africa", "from" : "Algeria", "to" : "Zimbabwe" }
{ "_id" : "Asia", "from" : "Afghanistan", "to" : "Yemen" }
{ "_id" : "Caribbean", "from" : "Antigua and Barbuda", "to" : "Trinidad and Tobago" }
{ "_id" : "Eurasia", "from" : "Armenia", "to" : "Russia" }
{ "_id" : "Europe", "from" : "Albania", "to" : "Vatican City" }
{ "_id" : "North America", "from" : "Belize", "to" : "United States" }
{ "_id" : "Oceania", "from" : "Australia", "to" : "Vanuatu" }
{ "_id" : "South America", "from" : "Argentina", "to" : "Venezuela" }
</syntaxhighlight>
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: "$continent"
}},
{$sort: {
_id: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$sort:{name:1}},{$group:{_id:'$continent',from:{$first:'$name'},to:{$last:'$name'}},},{$sort:{_id:1}}])</nowiki></pre>
</div>

==Countries beginning with...==
<div class="q" data-lang="mongo">
Group countries according to the first letter of the name. As shown.
Only give "U" through to "Z".

You will need to use the '''$substr''' function and the '''$push''' aggregate function.
<syntaxhighlight lang="JavaScript">
{ "_id" : "U", "list" : [ "Uganda", "Ukraine", "United Arab Emirates", "United Kingdom", "United States", "Uruguay", "Uzbekistan" ] }
{ "_id" : "V", "list" : [ "Vanuatu", "Vatican City", "Venezuela", "Vietnam" ] }
{ "_id" : "Y", "list" : [ "Yemen" ] }
{ "_id" : "Z", "list" : [ "Zambia", "Zimbabwe" ] }
</syntaxhighlight>
<pre class="def"><nowiki>
db.world.aggregate([
{$project: {
_id: '$name',
startsWith: {$substr: ['$name', 0, 1]}
}},
{$match: {
_id: {$gte: 'U'}
}},
{$sort: {_id: 1}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$group:{_id:{$substr:['$name',0,1]},list:{$push:'$name'}}},{$match:{_id:{$gte:'U'}}},{$sort:{_id:1}}]);</nowiki></pre>
</div>

==Harder Questions==
==Messing with continent names==
<div class="q" data-lang="mongo">
Combine <b>North America</b> and <b>South America</b> to <b>America</b>, and then list the continents by area. Biggest first.
<pre class="def"><nowiki>
db.world.aggregate([
{$group: {
_id: {
$cond: [
{$eq: ["$continent", "North America"]},
"America",
{$cond: [
{$eq: ["$continent", "Asia"]},
"The East",
"$continent"
]}
]
},
area: {$sum: "$area"}
}},
{$sort: {area: -1}},
{$project: {
_id: 1,
area: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$group":{"_id":{"$cond":[{"$eq":["$continent","South America"]},"America",{"$cond":[{"$eq":["$continent","North America"]},"America","$continent"]}]},"area":{"$sum":"$area"}}},{"$sort":{"area":-1}},{"$project":{"_id":1,"area":1}}]);</nowiki></pre>
</div>

==Messing with continent names 2==
<div class="q" data-lang="mongo">
Show the <b>name</b> and the <b>continent</b> for countries beginning with N - but replace the continent <b>Oceania</b> with <b>Australasia</b>.
<pre class="def"><nowiki>
db.world.aggregate([
{$match: {
name: {$regex: "^N"}
}},
{$project: {
_id: 0,
name: 1
}}
]);</nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$match":{"name":{"$regex":"^N"}}},{"$project":{"_id":0,"name":1,"continent":{"$cond":[{"$eq":["$continent","Oceania"]},"Australasia","$continent"]}}}]);</nowiki></pre>
</div>

==Messing with continent names 3==
<div class="q" data-lang="mongo">
Show the <b>name</b> and the <b>continent</b> but:<br/><br/>
*substitute <b>Eurasia</b> for <b>Europe</b> and <b>Asia</b>.<br/>
*substitute <b>America</b> - for each country in <b>North America</b> or <b>South America</b> or <b>Caribbean</b>.<br/><br/>Only show countries beginning with <b>A</b> or <b>B</b><br/>
If you're struggling you may want to experiment with <code>$and</code>,<code>$or</code>, etc.
<pre class="def"><nowiki></nowiki></pre>
<pre class="ans"><nowiki>db.world.aggregate([{$match:{name:{$regex:"^A|^B"}}},{$project:{_id:0,name:1,continent:{$cond:[{$or:[{$eq:["$continent","Europe"]},{$eq:["$continent","Asia"]}]},"Eurasia",{$cond:[{$or:[{$eq:["$continent","North America"]},{$eq:["$continent","South America"]},{$eq:["$continent","Caribbean"]}]},"America","$continent"]}]}}}]);</nowiki></pre>
</div>

==Messing with continent names 4==
<div class="q" data-lang="mongo">
Put the continents right...
<br/><br/>
*<b>Oceania</b> becomes <b>Australasia</b><br/>
*Countries in <b>Eurasia</b> and <b>Turkey</b> go to <b>Europe/Asia</b><br/>
*<b>Caribbean</b> islands starting with '<b>B</b>' go to <b>North America</b>, other Caribbean islands go to <b>South America</b><br/>
<br/><br/>
<b>Show the name, the original continent and the new continent of all countries.</b>
<pre class="def"></pre>
<pre class="ans"><nowiki>db.world.aggregate([{"$project":{"_id":0,"name":1,"original":"$continent","new":{"$cond":[{"$or":[{"$eq":["$continent","Eurasia"]},{"$eq":["$name","Turkey"]}]},"Europe/Asia",{"$cond":[{"$eq":["$continent","Oceania"]},"Australasia",{"$cond":[{"$and":[{"$eq":["$continent","Caribbean"]},{"$eq":[{"$substr":["$name",0,1]},"B"]}]},"North America",{"$cond":[{"$and":[{"$eq":["$continent","Caribbean"]},{"$ne":[{"$substr":["$name",0,1]},"B"]}]},"South America","$continent"]}]}]}]}}}]);</nowiki></pre>
</div>
[https://goo.gl/forms/ep8rBbCQSa381ic82 {{huge| Survey}}] <br/>
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FIND Tutorial

2020-11-21T19:56:45Z

Andr3w: /* Show Germany */

FIND Tutorial

2020-11-21T19:56:22Z

Andr3w: /* Show Germany */

==Working with the <code>world</code> collection of countries==
<p>
This tutorial introduces NoSQL using MongoDB. We will be using the <syntaxhighlight lang="JavaScript" inline>find()</syntaxhighlight >
command and comparison functions on the collection '''world''' which contains details of around 250 countries of the world:
</p>
[[FIND examples]] are available.
<div class='extra_space' style='width:1em; height:6em;'></div>
==Show Germany==
<div class="q" data-lang="mongo">
Use <syntaxhighlight lang="JavaScript" inline>find()</syntaxhighlight> to show the details of Germany.
<p class="strong">
Show Germany instead of France.
</p>
<pre class="def"><nowiki>db.world.find({name: 'France'});</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({name: 'Germany'});</nowiki></pre>
</div>

==Eurasia==
<div class="q" data-lang="mongo">
You can use <syntaxhighlight lang="JavaScript" inline>.pretty()</syntaxhighlight> to make the output more readable.
<p class="strong">
List all the countries in the continent of "Eurasia".
</p>
<pre class="def"><nowiki>db.world.find({name: 'Germany'}).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({continent: "Eurasia"}).pretty(); </nowiki></pre>
</div>

==Find an area==
<div class="q" data-lang="mongo">
You can test numbers as well as strings.
<p class="strong">
Find the country with an area of exactly 43094.
</p>
<pre class="def"><nowiki>db.world.find({gdp: 3425956000000}).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({area: 43094}).pretty(); </nowiki></pre>
</div>

==Using $gt==
<div class="q" data-lang="mongo">
You can use '''$gt''' (greater than) and '''$lt''' (less than) to compare numbers and strings.
<p class="strong">
Show each country with a population of over 250000000 <br/>
Sort the results alphabetically.
</p>
<p>You will need to use a [[FIND_Examples#Using_a_projection_with_find|projection]] to answer this question.</p>
<pre class="def"><nowiki>
db.world.find(
{area: {$gt: 9000000}},
{name: 1, _id: 0}
).sort(
{name: 1}
).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({population:{$gt:250000000}},{name:1,_id:0}).sort({name: 1}).pretty();</nowiki></pre>
</div>

==After S==
<div class="q" data-lang="mongo">
Greater than and less than comparisons can also be applied to strings.
<p class="strong">
List the countries that come after "S" in the alphabet.
</p>
<pre class="def"><nowiki>db.world.find();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({name:{$gt:"S"}},{name:1,_id:0}).pretty(); </nowiki></pre>
</div>

==Name and Capital==
<div class="q" data-lang="mongo">
<p class="strong">
Find the name and capital cities for countries with a population of over 70 million.
</p>
<pre class="def"><nowiki>db.world.findOne();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({population:{$gt:70000000}},{name:1,capital:1,_id:0}).pretty();</nowiki></pre>
</div>

==Using $or==
<div class=q data-lang=mongo>
<p class="strong">
Find the countries that have a population that is over 200 million or less than 20,000.
</p>
<pre class="def"><nowiki>
db.world.find(
{$or: [
{name: 'Germany'},
{name: 'France'}
]},
{name: 1, population: 1, _id: 0}
);</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({$or:[{population:{$gt:200000000}},{population:{$lt:20000}}]},{name:1,population:1,_id:0})</nowiki></pre>
</div>

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2020-10-25T15:23:04Z

Andr3w:

MediaWiki:Common.js

2020-10-25T15:19:33Z

Andr3w: Blanked the page

MediaWiki:Common.js

2020-10-25T13:18:31Z

Andr3w:

2019-09-25T08:58:19Z

Andr3w: /* Using $gt */

==Working with the <code>world</code> collection of countries==
<p>
This tutorial introduces NoSQL using MongoDB. We will be using the <syntaxhighlight lang="JavaScript" inline>find()</syntaxhighlight >
command and comparison functions on the collection '''world''' which contains details of around 250 countries of the world:
</p>
[[FIND examples]] are available.
<div class='extra_space' style='width:1em; height:6em;'></div>
==Show Germany==
<div class="q" data-lang="mongo">
Use <syntaxhighlight lang="JavaScript" inline>find()</syntaxhighlight> to show the details of Germany.
<p class="strong">
Show Germany instead of France.
</p>
<pre class="def"><nowiki>db.world.find({name: 'France'});</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({name: 'Germany'});</nowiki></pre>
</div>

==Eurasia==
<div class="q" data-lang="mongo">
You can use <syntaxhighlight lang="JavaScript" inline>.pretty()</syntaxhighlight> to make the output more readable.
<p class="strong">
List all the countries in the continent of "Eurasia".
</p>
<pre class="def"><nowiki>db.world.find({name: 'Germany'}).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({continent: "Eurasia"}).pretty();</nowiki></pre>
</div>

==Find an area==
<div class="q" data-lang="mongo">
You can test numbers as well as strings.
<p class="strong">
Find the country with an area of exactly 43094.
</p>
<pre class="def"><nowiki>db.world.find({gdp: 3425956000000}).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({area: 43094}).pretty();</nowiki></pre>
</div>

==Using $gt==
<div class="q" data-lang="mongo">
You can use '''$gt''' (greater than) and '''$lt''' (less than) to compare numbers and strings.
<p class="strong">
Show each country with a population of over 250000000 <br/>
Sort the results alphabetically.
</p>
<p>You will need to use a [[FIND_Examples#Using_a_projection_with_find projection]] to answer this question.</p>
<pre class="def"><nowiki>
db.world.find(
{area: {$gt: 9000000}},
{name: 1, _id: 0}
).sort(
{name: 1}
).pretty();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({population:{$gt:250000000}},{name:1,_id:0}).sort({name: 1}).pretty();</nowiki></pre>
</div>

==After S==
<div class="q" data-lang="mongo">
Greater than and less than comparisons can also be applied to strings.
<p class="strong">
List the countries that come after "S" in the alphabet.
</p>
<pre class="def"><nowiki>db.world.find();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({name:{$gt:"S"}},{name:1,_id:0}).pretty();</nowiki></pre>
</div>

==Name and Capital==
<div class="q" data-lang="mongo">
<p class="strong">
Find the name and capital cities for countries with a population of over 70 million.
</p>
<pre class="def"><nowiki>db.world.findOne();</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({population:{$gt:70000000}},{name:1,capital:1,_id:0}).pretty();</nowiki></pre>
</div>

==Using $or==
<div class=q data-lang=mongo>
<p class="strong">
Find the countries that have a population that is over 200 million or less than 20,000.
</p>
<pre class="def"><nowiki>
db.world.find(
{$or: [
{name: 'Germany'},
{name: 'France'}
]},
{name: 1, population: 1, _id: 0}
);</nowiki></pre>
<pre class="ans"><nowiki>db.world.find({$or:[{population:{$gt:200000000}},{population:{$lt:20000}}]},{name:1,population:1,_id:0})</nowiki></pre>
</div>

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