CASE Expression

The CASE Expression

Add conditional logic to your SQL queries with the CASE expression.

💡 CASE Expression are essential tools for handling conditional logic and NULL values in SQL.

CASE Syntax

-- Simple CASE (exact match)
CASE expression
    WHEN value1 THEN result1
    WHEN value2 THEN result2
    ELSE default_result
END

-- Searched CASE (conditions) 
CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ELSE default_result
END

Example

SELECT
    first_name,
    salary,
    CASE
        WHEN salary >= 80000 THEN 'High'
        WHEN salary >= 60000 THEN 'Medium'
        ELSE 'Low'
    END AS salary_level,
    ''
FROM employees;

✅ Key Takeaways

1. CASE adds if-then-else logic to SQL queries
2. CASE can be used in SELECT, WHERE, ORDER BY, and UPDATE
3. CASE has two forms: simple (exact match) and searched (conditions)
4. Always include an ELSE clause in CASE to handle unexpected values
5. CASE expressions can be nested for complex logic