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• Nov 9th, 2005

 

In database table design we are providing Primary key and Foreign keys.And according to primary and Foreign keys tables are functionaly dependent on each other.

jayaprakash.raman

 Profile Answers by jayaprakash.raman 

• Apr 24th, 2007

 

Normalization is the technique of breaking the complex tables into much understandable smaller one to improve the optimzation of the database structure. The concept of "Fucntional Dependancy" is followed in Second Normal Form (2NF) which means all the columns in the schema should be functionally dependent on the primary key of that schema. All the columns in the tables should have a relation ship with the main key. In this situation, all the columns are functionally dependednt.

Say for example, if you have an Employee table which has Empno, Ename, Salry columns. Here empno is the main key. Ename refers employee name and salary refers employee salary. Those are functionally dependent on Empno. If you include InvoiceNo in this table, it is irrelevent and also it is not functionally dependent on Empno.

As per Second Normal Form (2NF), all the non-functionally dependent columns to be removed from the schema and applied to the new table to increase the performance of the database.


-Jayaprakash Raman