Databases are characterized by a three-schema architecture because there are three different ways to look at them. Each schema is important to different groups in an organization. The figure illustrates this architecture and the groups most involved with each schema. |
Database management systems are often classified according to the database model that they support; the most popular database systems since the 1980s have all supported the relational model as represented by the SQL language. |
Why does it suck to be a penguin? Because even when you get angry, you still look cute. |