CASE is SQL's conditional expression - like IF-ELSE in programming. It evaluates conditions and returns different values based on which condition is TRUE.

**Two CASE Syntaxes:**

**Simple CASE:**

Compares expression to values:

CASE column

WHEN value1 THEN result1

WHEN value2 THEN result2

ELSE default_result

END

**Searched CASE:**

Evaluates boolean conditions:

CASE

WHEN condition1 THEN result1

WHEN condition2 THEN result2

ELSE default_result

END

**Key Concepts:**

• Evaluates top-to-bottom, stops at first TRUE

• ELSE clause is optional (returns NULL if no match)

• Can be used in SELECT, WHERE, ORDER BY, GROUP BY

• Returns single value per row

• All THEN results must be same data type

CASE is the SQL equivalent of IF-ELSE in programming. Critical for data analysts, BI developers, and backend engineers. Used in 80% of production queries for categorization, formatting, and conditional calculations.

CASE statements enable conditional logic in SQL - categorize data, transform values, handle NULL, create calculated fields. Used in every report, dashboard, and data transformation pipeline. Essential for business logic in queries.