Codd's 12 Rules for RDBMS
1. Information Rule : All information in a relational database are represented in form of table values.
2. Guaranteed Access Rule : Every piece (cell of table) of data in a relational database must be accessible. Means every cell of table must be accessible by using the name of table, name of column and primary key value of that record.
3. Systematic Treatment of Nulls Rule : The RDBMS should handles records that have unknown values in a predefined manner. Like Null in Oracle.
4. Active On-line catalog based on the relational model : The description of a database and in its contents are database tables and therefore can be queried on-line via the data manipulation language.
5. Comprehensive Data Sub-language Rule : A RDBMS may support several languages. But at least one of them should allow user to do all database operation like define tables and views, query and update the data, set integrity constraints, set authorizations and define transactions.
6. View Updating Rule : Any view that is theoretically update-able can be updated.
7. High-Level Insert, Update and Delete : The insert, update and delete on a table level should act on a set of records rather than one record at a time.
8. Physical Data Independence : Application programs is not affected by changes in the physical data access and storage methods.
9. Logical Data Independence : Logical changes in tables and views such adding/deleting columns or changing fields lengths need not necessitate modifications in the programs or in the format of adhoc requests.
10. Integrity Independence : Like table/view definition, integrity constraints are stored in the on-line catalog and can therefore be changed without necessitating changes in the application programs.
11. Distribution Independence : Application programs and adhoc requests are not affected by change in the distribution of physical data. If programs and data are moved in different sites.
12. No subversion Rule : If the RDBMS has a language that accesses the information of a record at a time, this language should not be used to bypass the integrity constraints.
2. Guaranteed Access Rule : Every piece (cell of table) of data in a relational database must be accessible. Means every cell of table must be accessible by using the name of table, name of column and primary key value of that record.
3. Systematic Treatment of Nulls Rule : The RDBMS should handles records that have unknown values in a predefined manner. Like Null in Oracle.
4. Active On-line catalog based on the relational model : The description of a database and in its contents are database tables and therefore can be queried on-line via the data manipulation language.
5. Comprehensive Data Sub-language Rule : A RDBMS may support several languages. But at least one of them should allow user to do all database operation like define tables and views, query and update the data, set integrity constraints, set authorizations and define transactions.
6. View Updating Rule : Any view that is theoretically update-able can be updated.
7. High-Level Insert, Update and Delete : The insert, update and delete on a table level should act on a set of records rather than one record at a time.
8. Physical Data Independence : Application programs is not affected by changes in the physical data access and storage methods.
9. Logical Data Independence : Logical changes in tables and views such adding/deleting columns or changing fields lengths need not necessitate modifications in the programs or in the format of adhoc requests.
10. Integrity Independence : Like table/view definition, integrity constraints are stored in the on-line catalog and can therefore be changed without necessitating changes in the application programs.
11. Distribution Independence : Application programs and adhoc requests are not affected by change in the distribution of physical data. If programs and data are moved in different sites.
12. No subversion Rule : If the RDBMS has a language that accesses the information of a record at a time, this language should not be used to bypass the integrity constraints.
posted by Unknown @ 16:32
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