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✅ Complete Roadmap to Learn SQL (Structured Query Language) 🧠💻 Week 1: SQL Basics - What is SQL and how databases work - Install MySQL Workbench or PostgreSQL - Learn SELECT, FROM, WHERE - Filtering data with conditions - Practice basic queries Example: Fetch all employees, filter salary > 50k Week 2: Sorting and Aggregation - ORDER BY (sorting data) - Aggregate functions: COUNT, SUM, AVG, MIN, MAX - GROUP BY concept - HAVING clause Example: Department-wise average salary Week 3: Joins (Most Important 🔥) - INNER JOIN - LEFT JOIN, RIGHT JOIN - FULL JOIN - Self Join Example: Combine employees and departments tables Week 4: Advanced Filtering - IN, BETWEEN, LIKE - Wildcards (% , _) - NULL handling (IS NULL, IS NOT NULL) - CASE statements Example: Categorize customers based on spending Week 5: Subqueries - Nested queries - Correlated subqueries - Using subqueries in SELECT, WHERE Example: Find employees earning above average salary Week 6: Window Functions (High Value 💰) - OVER() clause - ROW_NUMBER(), RANK(), DENSE_RANK() - PARTITION BY Example: Rank employees by salary within each department Week 7: CTE & Views - Common Table Expressions (WITH) - Temporary vs permanent views - Simplify complex queries Example: Multi-step data transformation Week 8: Data Modification - INSERT, UPDATE, DELETE - TRUNCATE vs DELETE - Constraints (PRIMARY KEY, FOREIGN KEY) Example: Update employee salary Week 9: Indexing & Performance - What are indexes - Query optimization basics - EXPLAIN keyword Example: Speed up large table queries Week 10: Working with Real Data - Import CSV data - Data cleaning in SQL - Handling duplicates - Basic transformations Example: Clean messy sales dataset Week 11: Mini Projects - Write complex queries - Solve real-world case studies - Focus on business logic Examples: Sales dashboard queries, Customer segmentation Week 12: Final Preparation - Revise all concepts - Practice interview questions - Solve SQL challenges on LeetCode / HackerRank - Mock interviews Daily Rule for You - Practice SQL 60 minutes daily - Solve 5 queries daily - Revise previous queries weekly 🔥 Pro Tip - Focus more on JOINS + WINDOW FUNCTIONS - Practice real datasets, not just theory - Think in terms of “business questions” Double Tap ❤️ For Detailed Explanation

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11:37

12.04.2026

𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝗲𝗿: You have 2 minutes to solve this SQL query. From the employees table, retrieve the employee name, department, and their salary rank within the department (highest salary rank 1). 𝗠𝗲: Challenge accepted!

    
        SELECT 
    name, 
    department, 
    salary,
    DENSE_RANK() OVER (PARTITION BY department ORDER BY salary DESC) AS salary_rank
FROM employees;{}

I applied DENSE_RANK() window function partitioned by department and ordered by descending salary to assign ranks within each department. Unlike ROW_NUMBER(), DENSE_RANK() handles ties by assigning the same rank without gaps. This is ideal for leaderboards or performance analytics. 𝗧𝗶𝗽 𝗳𝗼𝗿 𝗦𝗤𝗟 𝗝𝗼𝗯 𝗦𝗲𝗲𝗸𝗲𝗿𝘀: Master window function differences (ROW_NUMBER vs RANK vs DENSE_RANK)—they're interview staples for deduping, paging, and top-N queries! React with ❤️ for more

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