Methods Can add a method declaration with a structured type. method ageOnDate (onDate date) returns interval year Method body is given separately. create instance method ageOnDate (onDate date) returns interval year for CustomerType begin return onDate-self.dateOfBirth; end We can now find the age of each customer: select name.lastname,ageOnDate (current_date) from customer Database System Concepts-5th Edition,Aug 9,2005. 9.12 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 9.12 ©Silberschatz, Korth and Sudarshan th Edition, Aug 9, 2005. Methods Can add a method declaration with a structured type. method ageOnDate (onDate date) returns interval year Method body is given separately. create instance method ageOnDate (onDate date) returns interval year for CustomerType begin return onDate - self.dateOfBirth; end We can now find the age of each customer: select name.lastname, ageOnDate (current_date) from customer