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| If any of the one-to-many relationships are compromised, for e.g. an employee having more than one manager, the database structure switches from hierarchical to a network. A network database model is a database model that allows multiple records to be linked to the same owner file. The model can be seen as an upside down tree where the branches are the member information linked to the owner, which is the bottom of the tree. The multiple linkages which this information allows the network database model to be very flexible. In addition, the relationship that the information has in the network database model is defined as many-to-many relationship because one owner file can be linked to many member files and vice versa. The network database model was invented by Charles Bachman in 1969 as an enhancement of the already existing database model, the hierarchical database model. Because the hierarchical database model was highly flaw, Bachman decided to create a database that is similar to the hierarchical database but with more flexibility and less defaults. The original and existing hierarchical database has one owner file linked strictly to one member file, creating a ladder affect that restricted the database to find relationships outside of its category. Oracle Database 10g Express Edition (Oracle Database XE) is an entry-level, small-footprint database based on the Oracle Database 10g Release 2 code base that's free to develop, deploy, and distribute; fast to download; and simple to administer. Oracle Database XE is a great starter database for: * Developers working on PHP, Java, .NET, XML, and Open Source applications. |
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