PPT Slide

The Relational DBMS Revolution

• The pre-relational era (1970's)
  • Graph-based data models
    • Hierarchical (IMS), network (Codasyl)
  • Low-level, navigational interfaces
    • Labor-intensive and error-prone

• The relational era (1980's)
  • Simple, abstract data model
    • Database = set of relations ("tables")
    • 3 schema levels: views, base tables, physical schema
    • Algebra of set-oriented operations
  • High-level, declarative interfaces
    • SQL, QBE, et al
    • Embedded languages, 4GLs

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