HackerRank SQL Challenge Solutions

These are my solutions in SQL for all the challenges in HackerRank executed on MySQL, MS SQL Server and Oracle environments. These challenges cover topics like simple queries, sub-queries, aggregators, complex joins, unions, window functions and pivots in SQL.

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Description

These SQL challenges are categorized into 6 key domains (Basic Select, Advanced Select, Aggregation, Basic Join, Advanced Join and Alternative Queries) for all all easy, medium and hard levels.

Basic Select

Number	Challenges	Solutions	Max Score
1	Revising the Select Query I	File	10
2	Revising the Select Query II	File	10
3	Select All	File	10
4	Select By ID	File	10
5	Japanese Cities' Attributes	File	10
6	Japanese Cities' Names	File	10
7	Weather Observation Station 1	File	15
8	Weather Observation Station 3	File	10
9	Weather Observation Station 4	File	10
10	Weather Observation Station 5	File	10
11	Weather Observation Station 6	File	10
12	Weather Observation Station 7	File	10
13	Weather Observation Station 8	File	10
14	Weather Observation Station 9	File	10
15	Weather Observation Station 10	File	10
16	Weather Observation Station 11	File	10
17	Weather Observation Station 12	File	10
18	Higher Than 75 Marks	File	15
19	Employee Names	File	10
20	Employee Names	File	10

Advanced Select

Number	Challenges	Solutions	Max Score
Easy
1	Type of Triangle	File	10
Medium
1	The PADS	File	20
2	Occupations	File	30
3	Binary Tree Nodes	File	30
4	New Companies	File	30

Basic Join

Number	Challenges	Solutions	Max Score
Easy
1	Population Census	File	10
2	African Cities	File	10
3	Average Population of Each Continent	File	10
Medium
1	The Report	File	20
2	Top Competitors	File	30
3	Ollivander's Inventory	File	30
4	Challenges	File	30
5	Contest Leaderboard	File	30

Advanced Join

Number	Challenges	Solutions	Max Score
1	SQL Project Planning	File	40
2	Placements	File	40
3	Average Population of Each Continent	File	40

Aggregation

Number	Challenges	Solutions	Max Score
Easy
1	Revising Aggregations - The Count Function	File	10
2	Revising Aggregations - The Sum Function	File	10
3	Revising Aggregations - Averages	File	10
4	Average Population	File	10
5	Japan Population	File	10
6	Population Density Difference	File	10
7	The Blunder	File	15
8	Top Earners	File	20
9	Weather Observation Station 2	File	15
10	Weather Observation Station 13	File	10
11	Weather Observation Station 14	File	10
12	Weather Observation Station 15	File	15
13	Weather Observation Station 16	File	10
14	Weather Observation Station 17	File	15
Medium
1	Weather Observation Station 18	File	25
2	Weather Observation Station 19	File	30
3	Weather Observation Station 20	File	40

Alternative Queries

Number	Challenges	Solutions	Max Score
Easy
1	Draw The Triangle 1	File	25
2	Draw The Triangle 2	File	25
Medium
1	Print Prime Numbers	File	40