Post #2725

🔥 Let’s move to the next topic in the SQL Roadmap: ✅GROUP BY & Aggregation Functions 🧠 1. What is GROUP BY? GROUP BY is used to group rows with same values 👉 It helps you summarize data 💡 Example Table: employees name department salary Amit IT 60000 Neha HR 40000 Ravi IT 70000 Sara HR 50000 👉 Without GROUP BY SELECT AVG(salary) FROM employees; ✔ Gives overall average 👉 With GROUP BY SELECT department, AVG(salary) FROM employees GROUP BY department; ✔ Gives average salary per department ⚡ 2. Aggregation Functions These functions perform calculations on data 🔹 COUNT() → number of rows SELECT COUNT() FROM employees; 🔹 SUM() → total SELECT SUM(salary) FROM employees; 🔹 AVG() → average SELECT AVG(salary) FROM employees; 🔹 MIN() → smallest value SELECT MIN(salary) FROM employees; 🔹 MAX() → largest value SELECT MAX(salary) FROM employees; 🎯 3. GROUP BY + Aggregation 👉 Count employees in each department SELECT department, COUNT() FROM employees GROUP BY department; 👉 Total salary per department SELECT department, SUM(salary) FROM employees GROUP BY department; 👉 Highest salary per department SELECT department, MAX(salary) FROM employees GROUP BY department; 🚨 4. Important Rule (Interview Favorite) 👉 Every column in SELECT must be: - Either inside GROUP BY - Or used with aggregation function ❌ Wrong: SELECT name, AVG(salary) FROM employees; ✅ Correct: SELECT department, AVG(salary) FROM employees GROUP BY department; 🎯 5. Practice Tasks 1. Count total employees 2. Find total salary of all employees 3. Find average salary per department 4. Find maximum salary in each department 5. Count employees in each department ✅Practice Task Solution ✅ 1. Count total employees SELECT COUNT() FROM employees; ✅ 2. Find total salary of all employees SELECT SUM(salary) FROM employees; ✅ 3. Find average salary per department SELECT department, AVG(salary) FROM employees GROUP BY department; ✅ 4. Find maximum salary in each department SELECT department, MAX(salary) FROM employees GROUP BY department; ✅ 5. Count employees in each department SELECT department, COUNT() FROM employees GROUP BY department; ⚡ Mini Challenge 🔥 👉 Find department with highest average salary ⚡Mini Challenge Solution🔥 SELECT department, AVG(salary) AS avg_salary FROM employees GROUP BY department ORDER BY avg_salary DESC LIMIT 1; ⚡ Double Tap ❤️ For More