Motivation for Nesting Nesting of data is useful in data transfer Example:elements representing customer id,customer name,and address nested within an order element Nesting is not supported,or discouraged,in relational databases With multiple orders,customer name and address are stored redundantly normalization replaces nested structures in each order by foreign key into table storing customer name and address information Nesting is supported in object-relational databases But nesting is appropriate when transferring data External application does not have direct access to data referenced by a foreign key Database System Concepts-5th Edition,Aug 22,2005. 10.10 ©Silberschat乜，Korth and SudarshanDatabase System Concepts - 5 10.10 ©Silberschatz, Korth and Sudarshan th Edition, Aug 22, 2005. Motivation for Nesting Nesting of data is useful in data transfer Example: elements representing customer_id, customer_name, and address nested within an order element Nesting is not supported, or discouraged, in relational databases With multiple orders, customer name and address are stored redundantly normalization replaces nested structures in each order by foreign key into table storing customer name and address information Nesting is supported in object-relational databases But nesting is appropriate when transferring data External application does not have direct access to data referenced by a foreign key