I'm assuming that
customer_type may or may not contain the character 'B'.
For SQL Server
Code:
SELECT CASE customer_type
WHEN 'B' THEN 'Business'
ELSE 'Non Business'
END
FROM CUSTOMER_TABLE
OR
SELECT CASE WHEN customer_type = 'B' THEN 'Business'
ELSE 'Non Business'
END
FROM CUSTOMER_TABLE