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Day 30: Final Review & SQL Projects – Apply Your Knowledge! 🚀

🎉 Congratulations! You've reached the final day of your 30-day SQL journey. Today, we’ll:

✅ Review all key SQL concepts learned over the past 30 days.
✅ Work on real-world SQL projects to apply your skills.
✅ Solve case studies & challenges to test your knowledge.

By the end of this lesson, you’ll be confident in writing SQL queries and solving real-world data problems!

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🔹 Quick Recap: Key SQL Concepts You Learned

| Topic | Key Learnings |
|-----------|------------------|
| Day 1-5: Basics | SQL syntax, SELECT, WHERE, ORDER BY, GROUP BY, HAVING, Aggregate Functions |
| Day 6-10: Joins & Subqueries | INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN, Subqueries |
| Day 11-15: Advanced Queries | Common Table Expressions (CTEs), Window Functions, Case Statements |
| Day 16-20: Views, Transactions, Indexing | Creating Views, Indexing, Transactions & ACID properties, Error Handling |
| Day 21-25: Database Design & Security | Normalization (1NF, 2NF, 3NF, BCNF), Constraints, Backup & Restore, Role-Based Permissions |
| Day 26-29: Performance Optimization | Pivoting, JSON/XML in SQL, Stored Procedures, Triggers, Query Performance Tuning |

If you’ve completed all the lessons, you now have a solid SQL foundation! 🏆

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🔹 Real-World SQL Projects & Case Studies

Now, let’s apply what you’ve learned by working on SQL projects.

Project 1: Analyzing Sales Data 📊

Scenario: You work for an e-commerce company, and management wants to analyze sales performance.

Dataset: Sales Table
| SaleID | Date | CustomerID | ProductID | Quantity | Price | TotalAmount |
|--------|------|------------|------------|---------|------|------------|
| 101 | 2024-01-10 | 1 | 1001 | 2 | 500 | 1000 |
| 102 | 2024-01-11 | 2 | 1002 | 1 | 300 | 300 |
| 103 | 2024-01-12 | 1 | 1003 | 5 | 200 | 1000 |

Tasks:
✔️ Find total sales per customer

SELECT CustomerID, SUM(TotalAmount) AS TotalSpent  
FROM Sales  
GROUP BY CustomerID  
ORDER BY TotalSpent DESC;

✔️ Get the top 5 products by sales revenue

SELECT ProductID, SUM(TotalAmount) AS Revenue  
FROM Sales  
GROUP BY ProductID  
ORDER BY Revenue DESC  
LIMIT 5;

✔️ Find the total revenue for each month

SELECT DATE_FORMAT(Date, '%Y-%m') AS Month, SUM(TotalAmount) AS Revenue  
FROM Sales  
GROUP BY Month  
ORDER BY Month;

✔️ Find customers who made purchases in January but not in February

SELECT DISTINCT CustomerID  
FROM Sales  
WHERE DATE_FORMAT(Date, '%Y-%m') = '2024-01'  
AND CustomerID NOT IN (  
    SELECT DISTINCT CustomerID FROM Sales  
    WHERE DATE_FORMAT(Date, '%Y-%m') = '2024-02'  
);

🎯 Objective: Gain hands-on experience analyzing business sales data.

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Project 2: Building a Reporting Dashboard 📊

🔹 Tools: Use SQL with Power BI, Tableau, or Python (Pandas & Matplotlib)

✔️ Step 1: Write SQL queries to extract data from your database.
✔️ Step 2: Connect SQL with Power BI/Tableau to create reports.
✔️ Step 3: Build visualizations (e.g., bar charts, trend lines, KPIs).

🎯 Objective: Convert raw data into actionable insights for decision-making.

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Project 3: Employee Management System

Scenario: HR wants to track employee performance and salaries.

Dataset: Employees Table
| EmpID | Name | Department | Salary | JoinDate |
|--------|------|------------|--------|---------|
| 1 | Alice | IT | 80000 | 2021-05-10 |
| 2 | Bob | HR | 60000 | 2022-08-15 |
| 3 | Charlie | IT | 90000 | 2019-12-01 |

Tasks:
✔️ Find average salary by department

SELECT Department, AVG(Salary) AS AvgSalary  
FROM Employees  
GROUP BY Department;

✔️ List employees who have been with the company for more than 3 years

SELECT Name, JoinDate  
FROM Employees  
WHERE JoinDate <= DATE_SUB(CURDATE(), INTERVAL 3 YEAR);

✔️ Create a stored procedure to update salaries based on department

DELIMITER //  
CREATE PROCEDURE UpdateSalaries()  
BEGIN  
    UPDATE Employees SET Salary = Salary * 1.10 WHERE Department = 'IT';  
END //  
DELIMITER ;

🎯 Objective: Learn how to manage employee data using SQL.

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