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. |
“Whenever you find yourself on the side of the majority, it is time to reform (or pause and reflect).” ― Mark Twain |