Object-relational database

Object-relational database

1. Features

   • Advantages
     • Ease of use
     • Flexibility
     • Precision
     • Security
     • Data Independence
     • Data Manipulation Language
   • Disadvantages
     • machine performance
     • Schema Changes
     • Language Dependence
     • Lack of Ad-Hoc Queries

2. object types

   • model real-world entities
   • Object Columns
     • An object column is a column in a table that is defined using an object type.
   • Object Tables
     • object table is a table in which each row contains one object of a given object type.

3. NULL

   • atomic NULL
     • object can be atomically NULL
       • cannot be updated
   • NULL attributes
     • object can have attributes that are NULL
       • Updates on its individual attributes
         • Must use cascade clause

4. collection types

   • VARRAY
     • variable sized array which has ordered set of data elements of the same type.
   • Nested tables
     • Tables are ordered set of elements of the same data type