Re: Pls help!!!!

Rule 4: Dynamic On-Line Catalog Based on the Relational Model A relational database must provide access to its structure through the same tools that are used to access the data. This is usually accomplished by storing the structure definition within special system tables.

This is the Meta data or data about data. Oracle maintains system catalogs and one can get information from them just the same way you get information from other tables.

Rule 6: View Updating Rule
Data can be presented to the user in different logical combinations, called views. Each view should support the same full range of data manipulation that direct-access to a table has available. In practice, providing update and delete access to logical views is difficult and is not fully supported by any current database.

Oracle has views. Simple views can easily be updated, inserted, deleted, complex views need instead of triggers written, but they can be inserted, updated, deleted.

Rule 7: High-level Insert, Update, and Delete Data can be retrieved from a relational database in sets constructed of data from multiple rows and/or multiple tables. This rule states that insert, update, and delete operations should be supported for any retrievable set rather than just for a single row in a single table.

This is the whole thing Codd is getting at - data is treated as tuples or sets.

How's the homework coming along?
Jim

"Joachim Kjær" <kjaerhome_at_get2net.dk> wrote in message news:5p4M7.41$a61.1232_at_news.get2net.dk...
> Hello,
>
> Can any one help me understand codd's rule 4, 6 and 7?
>
> And does Oracle fulfil all Codd rules, if not which one does it not
fulfil?
>
> Hope someone can help me :o)
>
> Hopefull regards - Tilda
>
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Received on Sun Nov 25 2001 - 10:07:37 CST