The SQL CASE Expression
The CASE expression is used to define different results based on specified conditions in an SQL statement.
The CASE expression goes through the conditions and stops at the first match (like an if-then-else statement). So, once a condition is true, it will stop processing and return the result. If no conditions are true, it returns the value in the ELSE clause. If there is no ELSE clause and no conditions are true, it returns NULL.
CASE Syntax
CASE WHEN
condition1
THEN
result1
WHEN
condition2
THEN
result2
WHEN
conditionN
THEN
resultN
ELSE
default_result
END;SQL CASE Example
Here we use the CASE expression to categorize data (Price) and we create a new column (PriceCategory) that shows in which price category each product is:
Example
SELECT ProductName, Price,
CASE
WHEN Price < 20 THEN 'Low Cost'
WHEN Price BETWEEN 20 AND 50 THEN 'Medium Cost'
ELSE 'High Cost'
END AS PriceCategory
FROM Products;