Linux Journal: Linux and Databases

“A preview and summary of the May 2 episode of Phil Hughes’
weekly radio program featured on Wall Street News Hour.”

“There are three categories of database worth looking at that
are, or have been, in common usage. Importantly, many contemporary
DBMSes may offer one, two or a combination of all three databasing
methods.

• Hierarchical databases. These are the oldest of the modern
  computer databases (as opposed to the ancient computer databases,
  right?) and may be what most people, when asked, imagine a database
  to be. A hierarchical database is arranged something like an
  inverted family tree; access to the database begins at the top of
  the hierarchy and moves downward. …
• Relational databases. Relational databases are all the rage in
  terms of database efficiency and power. In fact, most of the
  databases mentioned toward the end of this discussion —
  PostgreSQL, Interbase, IBM DB2 — are relational databases. … By
  way of analogy, if a hierarchical database represents “getting out
  only what you put in (and only in the form in which the data was
  entered)”, then a relational database offers the ability to get,
  effectively, information that was not specifically “entered” into
  the database. …
• Network databases. There are a number of definitions for
  network databases, but the one that is probably most relevant here
  is the one that explains network databases as data organization
  methods in which data relationships have a “net-like” or
  hyperlinked character. …”

Complete
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