This repository contains my journey through SQL challenges on HackerRank, where I earned a 5-star rating in SQL programming. Each solution demonstrates different aspects of SQL querying, from basic SELECT statements to advanced window functions, aggregations, and complex joins. These solutions are compatible with MySQL, PostgreSQL, and SQL Server.

• SelectAll.sql - Basic SELECT statement for all columns
• SelectByID.sql - Filtering with WHERE clause using specific ID
• SelectQueryI.sql - Multiple conditions with AND operator
• SelectQueryII.sql - Selecting specific columns with conditions
• JapaneseCitiesNames.sql - Filtering by country code
• JapaneseCitiesAttributes.sql - All attributes for specific country

• RevisingAggregationsTheCountFunction.sql - COUNT function with conditions
• RevisingAggregationsTheSumFunction.sql - SUM function with filtering
• RevisingAggregationsAverages.sql - AVG function for statistical analysis
• AveragePopulations.sql - ROUND function with AVG
• JapanPopulations.sql - SUM aggregation with country filter
• PopulationDensityDifference.sql - MAX and MIN functions

• WeatherObservationStation1.sql - Basic multi-column selection
• WeatherObservationStation2.sql - ROUND function with SUM
• WeatherObservationStation3.sql - Modulo operator for even IDs
• WeatherObservationStation4.sql - COUNT vs COUNT DISTINCT
• WeatherObservationStation5.sql - LENGTH function with ORDER BY and LIMIT
• WeatherObservationStation6.sql - LIKE operator for vowel patterns
• WeatherObservationStation7.sql - SUBSTR function for ending characters
• WeatherObservationStation8.sql - LEFT and RIGHT functions
• WeatherObservationStation9.sql - NOT IN with SUBSTR for consonants
• WeatherObservationStation10.sql - String ending conditions
• WeatherObservationStation11.sql - OR conditions with string functions
• WeatherObservationStation12.sql - Complex NOT IN conditions

• WeatherObservationStation13.sql - TRUNCATE with range conditions
• WeatherObservationStation14.sql - MAX with TRUNCATE function
• WeatherObservationStation15.sql - Subquery with MAX and conditions
• WeatherObservationStation16.sql - MIN with ROUND and range
• WeatherObservationStation17.sql - Subquery with MIN in WHERE clause
• WeatherObservationStation18.sql - Manhattan distance calculation
• WeatherObservationStation19.sql - Euclidean distance with SQRT and POWER
• WeatherObservationStation20.sql - Median calculation using subqueries

• EmployeeNames.sql - Basic ORDER BY for sorting
• EmployeeSalaries.sql - Multiple conditions with AND
• TopEarners.sql - MAX function with subquery and COUNT
• NewCompanies.sql - Complex JOIN with GROUP BY and COUNT DISTINCT

• HigherThan75Marks.sql - SUBSTR for sorting by last 3 characters
• ThePADS.sql - CONCAT function with string formatting
• TheBlunder.sql - REPLACE function with mathematical operations

• TypeofTriangle.sql - Nested CASE statements for triangle classification
• BinaryTreeNode.sql - CASE with subqueries for tree node classification
• Occupation.sql - PIVOT operations with ROW_NUMBER() window function

• SELECT, FROM, WHERE clauses
• Filtering with conditions (=, >, <, >=, <=, <>)
• Logical operators (AND, OR, NOT)
• DISTINCT for unique values

• LIKE patterns with wildcards (%, _)
• SUBSTR() / SUBSTRING() for character extraction
• LEFT() and RIGHT() functions
• CONCAT() for string concatenation
• REPLACE() for character substitution
• LENGTH() for string length

• COUNT(), SUM(), AVG(), MAX(), MIN()
• GROUP BY for data grouping
• HAVING clause for filtered aggregations

• ROUND(), TRUNCATE(), CEIL(), FLOOR()
• SQRT(), POWER() for calculations
• Mathematical operators (+, -, *, /, %)

• Subqueries and correlated subqueries
• Window functions (ROW_NUMBER(), OVER())
• CASE statements for conditional logic
• PIVOT operations for data transformation
• JOIN operations (LEFT JOIN)

• MySQL syntax and functions
• PostgreSQL compatibility
• SQL Server T-SQL features
• Standard SQL compliance

1. Clone the repository:

   git clone https://github.com/yourusername/SQL-with-Problem-Solving.git
   cd SQL-with-Problem-Solving

2. Execute any solution:

   -- Copy the SQL code from any .sql file
   -- Run it in your preferred SQL environment (MySQL, PostgreSQL, SQL Server)

3. Example execution:

   -- From SelectAll.sql
   SELECT * FROM CITY;

Category	Problems Solved	Difficulty	Key Concepts
Basic Select	6	🟢 Easy	SELECT, WHERE, filtering
Advanced Select	5	🟡 Medium	String functions, patterns
Aggregation	6	🟡 Medium	COUNT, SUM, AVG, GROUP BY
Weather Stations	20	🟡 Medium	String manipulation, math functions
Join Operations	1	🔴 Hard	LEFT JOIN, GROUP BY
Advanced Topics	7	🔴 Hard	CASE, subqueries, window functions

• ✅ Proficiency in SQL query writing and optimization
• ✅ String manipulation and pattern matching expertise
• ✅ Advanced aggregation and mathematical functions
• ✅ Subquery design and correlated queries
• ✅ Window functions and analytical queries
• ✅ Database schema understanding and relationships
• ✅ Performance optimization techniques
• ✅ Cross-platform SQL compatibility

• Basic and advanced SELECT statements
• Multi-table queries with JOINs
• Filtering and sorting large datasets

• Statistical calculations (averages, medians, ranges)
• Distance calculations (Manhattan, Euclidean)
• Pattern recognition and classification

• Text pattern matching and extraction
• Character-based filtering and sorting
• String formatting and manipulation

• Employee hierarchy analysis
• Geographic data processing
• Educational grading systems

• HackerRank Profile: Your HackerRank Profile
• LinkedIn: Your LinkedIn Profile
• GitHub: Your GitHub Profile

This project is licensed under the MIT License - see the LICENSE file for details.

Feel free to fork this repository and submit pull requests for any improvements or additional solutions! Contributions for SQL optimization or alternative approaches are welcome.

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