"satish mullapudi" <sa***************@gmail.comwrote in message
news:11**********************@q75g2000hsh.googlegr oups.com...
>I have found out that an RDBMS implements the relational model
designed by Codd for which he designed 12 rules. These r nicknamed as
" Codd Rules".
Are these rules similar to Normalization rules which we follow ? And
does Referential Integrity has a anything to do with Relational-DB ?
Awaiting ur replies...
satish
No, relational is not the same as normalization. However, relational set
theory works best if data is normalized to 3rd normal form. Also, most
relational databases do not support repeating groups within a table (or
record), which is fundamental principal of 3rd normal form (not to have
repeating groups) so to some degree relational "helps" enforce a certain
level of normalization.
The concept of referential integrity pre-dates relational databases.
Relational databases share very similar terminology and SQL syntax, so that
they have similar concepts and syntax for declaring referential integrity
within the database using DDL. Databases which pre-date relational may also
have the concept of referential integrity (such as IDMS), but they use
different terminology and use different mechanisms to define RI in the
physical design.
If you look at Codd's 12 rules, the best way to summarize most of them is to
say that a database is relational to the extent that the physical
implementation of data is hidden from the logical view of the data. In a
relational database, the user accesses data via tables and columns, and does
not have to worry about things like access path or indexes to get the
correct answer (even though DBA's have to worry about it to get good
performance).