✅ 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”

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