<P> Student_Type then could be used in order to create a Student_Table which will include all columns defined in Person_Type as well . Primary Key and Constraints should be defined during or after creation of table and cannot be defined inside structure type itself . </P> <P> Each custom structure type can also contain other types in order to support more complex structures: </P> <Ul> <Li> Jim Melton (2003). Advanced SQL: 1999 . Morgan Kaufmann . ISBN 978 - 1 - 55860 - 677 - 7 . Chapters 2 - 4 . </Li> <Li> Suzanne W. Dietrich; Susan D. Urban (2011). Fundamentals of Object Databases: Object - Oriented and Object - Relational Design . Morgan & Claypool Publishers . ISBN 978 - 1 - 60845 - 476 - 1 . Chapter 3 . </Li> <Li> Catherine Ricardo (2011). Databases Illuminated (2nd ed .). Jones & Bartlett Publishers . ISBN 978 - 1 - 4496 - 0600 - 8 . Chapter 8 . </Li> </Ul> <Li> Jim Melton (2003). Advanced SQL: 1999 . Morgan Kaufmann . ISBN 978 - 1 - 55860 - 677 - 7 . Chapters 2 - 4 . </Li>

What is a structured data type in oracle