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LatestCodd's 12th Rule

LatestCodd's 12th Rule - Codd’s 12 Rule Codd’s th...

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Unformatted text preview: Codd’s 12 Rule Codd’s th Presented by, Doshi Maulik B. Zanzaria Gaurav O. Korvadia Ankur V. Enti Sandeep Reddy Katewa Anuj Akhil Prasad Pitta Codd’s Vision Codd’s Dr. E. F. Codd Born 1932, UK. Died April 18, 2003. BA/MA (Maths) Oxford University PhD University of Michigan. It provides a means of It describing data with its natural structure only i.e. without superimposing any additional structure for machine representation purpose. Accordingly, it provides a Accordingly, basis for a high level data language which will yield maximal independence between programs on one hand and machine representation on the other. representation Overview of Codd’s Rules Overview Rule 0 : Foundation Rule – Each RDBMS has to manage all the databases entirely Each through its relational capabilities. through Rule 1 : Information Rule – Everything within the database exists in tables and is Everything accessed via table access routines. Rule 2 : Guaranteed Access Rule – To access any data-item you specify which column To within which table it exists. within Rule 3 : Systematic treatment of null values. – If data does not exist or does not apply then a value of If NULL is applied by RDBMS. NULL Overview of Codd’s Rules Overview Rule 4 : Dynamic on­line catalog based on the relational model. – The Data Dictionary is held within the RDBMS, thus there is The no-need for off-line volumes to tell you the structure of the database. database. Rule 5 : Comprehensive data sub­language Rule. – Every RDBMS should provide a language to allow the user to Every query the contents of the RDBMS and also manipulate the contents of the RDBMS. contents Rule 6 : View updating Rule – Not only can the user modify data, but so can the RDBMS Not when the user is not logged-in. when Rule 7 : High­level insert, update and delete. – The user should be able to modify several tables by The modifying the view to which they act as base tables. modifying Overview of Codd’s Rules Overview Rule 8 : Physical data independence. – The user should not be aware of where or upon which media The data-files are stored. data-files Rule 9 : Logical data independence. – User programs and the user should not be aware of any User changes to the structure of the tables. changes Rule 10 : Integrity independence. – If a column only accepts certain values, then it is the RDBMS If which enforces these constraints and not the user program. which Rule 11 : Distribution independence. – The RDBMS may spread across more than one system and The across several networks, however to the end-user the tables should appear no different to those that are local. should Codd’s 12 Rule: Non Subversion Codd’s th “If a relational system has a low-level If (single-record-at-a-time) language, that low level cannot be used to subvert or bypass the integrity Rules and constraints expressed in the higher level relational language (multiple-records-at-a-time).” language Example Example Low Level accesses – Back up. – Load Utility. Prevents from bypassing – Authentication – Constraints and – Locks. Summary Summary It prevents other path into the database that It might subvert the relational structure and integrity. integrity. The RDBMS should prevent users from The accessing the data without going through the data-read functions. the Condition for RDBMS Condition Any RDBMS Product has to satisfy at least Any six of twelve rules of Codd to be accepted as a full fledged RDBMS. as Deficiency in Codd’s Rules Deficiency Not all the Rules are getting followed by any Not RDBMS System. Example: Oracle 9i follows 11.5 Rules. Example: Modeling of present day’s RDBMS is not Modeling only limited to Codd’s 12 Rules because RDBMS is not only for Data Storage. RDBMS ...
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