5.2 Architecture of a Relational Database Management System (RDBMS)
Relational database management systems (RDBMSs) support the standard three-level architecture for databases. As shown in FIGURE 5.1, relational databases provide both logical and physical data independence because they separate the external, logical, and internal levels. The logical level for relational databases consists of base tables that are physically stored. These tables are created by the database administrator (DBA) using a CREATE TABLE command, as described in Section 5.3. A base table can have any number of indexes, either created by the system itself or created by the DBA using the CREATE INDEX command. An index is used to speed up retrieval of records based on the ...
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