✅ CASE Statement in SQL

 

✅ CASE Statement in SQL  

🧠 1. What is CASE Statement?

• CASE is used for conditional logic in SQL
• It's like if-else in programming
• Helps categorize data
• Create custom labels
• Build smart reports  

⚡ 2. Basic Syntax

SELECT column_name,

       CASE

           WHEN condition THEN result

           ELSE result

       END AS alias_name

FROM table_name;

📊 Example Table  

name : Ajit, Neha, Sujit  

salary : 70000, 40000, 55000  

🔥 3. Basic CASE Example  

👉 Categorize employees by salary

SELECT name, salary,

       CASE

           WHEN salary >= 60000 THEN 'High Salary'

           WHEN salary >= 50000 THEN 'Medium Salary'

           ELSE 'Low Salary'

       END AS salary_category

FROM employees;

✅ Output  

name : Ajit, Sujit, Neha  

salary : 70000, 55000, 40000  

salary_category : High Salary, Medium Salary, Low Salary  

⚡ 4. CASE with Aggregation  

👉 Count employees department-wise

SELECT department,

       SUM(

           CASE

               WHEN salary > 50000 THEN 1

               ELSE 0

           END

       ) AS high_salary_count

FROM employees

GROUP BY department;

⚡ 5. CASE in ORDER BY

SELECT name, department

FROM employees

ORDER BY

CASE

    WHEN department = 'IT' THEN 1

    WHEN department = 'HR' THEN 2

    ELSE 3

END;

🎯 6. Practice Tasks

1. Categorize salary as High/Low

2. Create age groups using CASE

3. Use CASE with GROUP BY

4. Count employees based on salary condition

5. Use CASE in ORDER BY

What will this query return?

SELECT name, salary,

       CASE

           WHEN salary >= 50000 THEN 'High'

           ELSE 'Low'

       END AS category

FROM employees;

A. Deletes salaries

B. Sorts employees

C. Add employees

D. Categorizes salary as High or Low

Ans : D