SQL CASE Statement

💻 Introduction

The CASE statement in SQL lets you add conditional logic inside your queries. It works like an IF-THEN-ELSE statement and returns values based on conditions.

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1️⃣ Simple CASE Expression

Matches a column against specific values.

SELECT EmpID, FirstName, 
       CASE Department
            WHEN 'HR' THEN 'Human Resources'
            WHEN 'IT' THEN 'Technology'
            WHEN 'FIN' THEN 'Finance'
            ELSE 'Other'
       END AS Department_Name
FROM Employees;

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2️⃣ Searched CASE Expression

Uses logical conditions instead of direct matching.

SELECT EmpID, Salary,
       CASE 
            WHEN Salary > 100000 THEN 'High'
            WHEN Salary BETWEEN 50000 AND 100000 THEN 'Medium'
            ELSE 'Low'
       END AS Salary_Level
FROM Employees;

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3️⃣ CASE in ORDER BY

You can use CASE to control sorting order dynamically.

SELECT EmpID, FirstName, Department
FROM Employees
ORDER BY 
    CASE Department
        WHEN 'HR' THEN 1
        WHEN 'IT' THEN 2
        ELSE 3
    END;

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✅ Key Takeaways

• Simple CASE → Compare a column to specific values.
• Searched CASE → Use conditions like >, <, BETWEEN.
• CASE can be used in SELECT, ORDER BY, GROUP BY.
• Acts like IF-ELSE in SQL queries.

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