How can you use the CASE clause for conditional selection?

Q: How can you use the CASE clause for conditional selection?

In MySQL, the **CASE clause** allows you to perform conditional logic directly within a query. It can be used in SELECT, ORDER BY, GROUP BY, or even WHERE clauses to return values based on conditions. Evaluates conditions sequentially and returns the value for the first true condition. Supports a default result using the `ELSE` keyword if none of the conditions match. Can be used to categorize data or perform conditional calculations in the result set. Syntax: ``` CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE result_default END ``` The CASE clause is extremely useful for transforming data on the fly, creating computed columns, or applying conditional logic without changing the underlying data. SELECT name, salary, CASE WHEN salary >= 100000 THEN 'High' WHEN salary >= 50000 THEN 'Medium' ELSE 'Low' END AS salary_category FROM employees;

Difficulty: 5/10

conditional logic, query optimization, maintainability

Using the CASE Clause in MySQL

In MySQL, the CASE clause allows you to perform conditional logic directly within a query. It can be used in SELECT, ORDER BY, GROUP BY, or even WHERE clauses to return values based on conditions.

Key Features of the CASE Clause

1
Evaluates conditions sequentially and returns the value for the first true condition.
2
Supports a default result using the ELSE keyword if none of the conditions match.
3
Can be used to categorize data or perform conditional calculations in the result set.

Syntax:

CASE
  WHEN condition1 THEN result1
  WHEN condition2 THEN result2
  ELSE result_default
END

The CASE clause is extremely useful for transforming data on the fly, creating computed columns, or applying conditional logic without changing the underlying data.

Example of CASE Clause Usage

Scenario Questions

0-2 years experience

2-5 years experience

Follow-up Questions