BranchesTags

Repository files navigation

HackerRank logo

Solutions to HackerRank challenges

This repository is a collection of updated solutions to programming challenges on HackerRank.

SQL / MySQL

I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.

Basic Select

ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution

Advanced Select

ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution

Aggregation

ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution

Basic Join

ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution

Advanced Join

ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution

Alternative Queries

ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Contact me

Feel free to connect with me on LinkedIn: Reyas Khan

If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.

Happy learning

HackerRank-solutions-SQL

About

Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.

Topics

certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling

Resources

Readme
MIT license
Activity

Stars

0 stars

Watchers

1 watching

Forks

0 forks
Report repository

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Contributors

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
BranchesTags
Repository files navigation
HackerRank logo
Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Solutions to HackerRank challenges
This repository is a collection of updated solutions to programming challenges on HackerRank.
SQL / MySQL
I have used MYSQL for the solutions. There are almost always multiple solutions to the same problem. I have tried including alternate solutions whenever possible.
Basic Select
ChallengeScoreSolution
Revising the Select Query I10Solution
Revising the Select Query II10Solution
Select All10Solution
Select By ID10Solution
Japanese Cities' Attributes10Solution
Japanese Cities' Names10Solution
Weather Observation Station 115Solution
Weather Observation Station 310Solution
Weather Observation Station 410Solution
Weather Observation Station 530Solution
Weather Observation Station 610Solution
Weather Observation Station 710Solution
Weather Observation Station 815Solution
Weather Observation Station 910Solution
Weather Observation Station 1010Solution
Weather Observation Station 1115Solution
Weather Observation Station 1215Solution
Higher Than 75 Marks15Solution
Employee Names10Solution
Employee Salaries10Solution
Advanced Select
ChallengeScoreSolution
Type of Triangle20Solution
The PADS30Solution
Occupations30Solution
Binary Tree Nodes30Solution
New Companies30Solution
Aggregation
ChallengeScoreSolution
Revising Aggregations - The Count Function10Solution
Revising Aggregations - The Sum Function10Solution
Revising Aggregations - Averages10Solution
Average Population10Solution
Japan Population10Solution
Population Density Difference10Solution
The Blunder15Solution
Top Earners20Solution
Weather Observation Station 215Solution
Weather Observation Station 1310Solution
Weather Observation Station 1410Solution
Weather Observation Station 1515Solution
Weather Observation Station 1610Solution
Weather Observation Station 1715Solution
Weather Observation Station 1825Solution
Weather Observation Station 1930Solution
Weather Observation Station 2040Solution
Basic Join
ChallengeScoreSolution
Asian Population10Solution
African Cities10Solution
Average Population of Each Continent10Solution
The Report20Solution
Top Competitors30Solution
Ollivander's Inventory30Solution
Challenges30Solution
Contest Leaderboard30Solution
Advanced Join
ChallengeScoreSolution
SQL Project Planning40Solution
Placements40Solution
Symmetric Pairs40Solution
Interviews50Solution
15 Days of Learning SQL50Solution
Alternative Queries
ChallengeScoreSolution
Draw The Triangle 125Solution
Draw The Triangle 225Solution
Print Prime Numbers40Solution
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Contact me
Feel free to connect with me on LinkedIn: Reyas Khan
If you have any questions, doubts, or would like to discuss anything related to this Challenge, don't hesitate to reach out! I'm always happy to help.
Happy learning
HackerRank-solutions-SQL
About
Welcome to the HackerRank SQL Solutions Repository! This repository contains my solutions to various SQL challenges from HackerRank.
Topics
certify-maintenancehackerrankhackerrank-solutionshackerrank-sqlhackerrank-sql-certificatehackerrank-sql-challengelearning-exercisemysqlsqlupskilling
Resources
Readme
MIT license
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Releases
Packages
Contributors