Eliminate repeating groups, Database Management System

Eliminate Repeating Groups

The problem is, "Find out the list of employees, who knows DB2".

For this problem we require to perform an awkward scan of the list looking for references to DB2. This is ineffective and a very untidy way to retrieve information.

We change the relation to 1NF. Please note that in the Department-loc fields and conversion Department will be part of Employee relation. The Emp-ID in the Database relation matches the primary key in the employee relation, giving a foreign key for relating the two relations with a join operation. Now we can response the question by looking in the database relation for "DB2" and getting the list of Employees. Please note that in this design we require not add D-ID (Database ID). Just the name of the database would have been sufficient as the names of databases are original.

Employee Relation

 

 

Database Relation

Emp-ID

Emp-Name

D-ID

Emp-ID

Database-name

1

Gurpreet Malhotra

1

2

Access

2

Faisal Khan

2

4

DB2

3

Manisha Kukreja

3

3

FoxPro

4

Sameer Singh

4

1

Oracle

 

4

4

Oracle

Posted Date: 3/7/2013 2:26:24 AM | Location : United States







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