This will allow you to store
CUSTOMER_REVENUE_LAST_YEAR in a
DECIMAL(9,3) field that takes up only 4 Byte. Without the use of the capping functions, a customer with 1.000.000,00 EUR of revenue would have caused a numeric overflow error. You would have been forced to use a
DECIMAL(10,3) or bigger, which would use 8 Byte per record. Of course, this is only an option when the exact value of the revenue per customer is not critically important. In a financial report, just capping the revenue would be very problematic. When using it as a feature in a machine learning product, it typically is not.