Page 137 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Database Management Systems/Managing Database

Notes
Example: Consider an Employee table with an attribute Dependents as shown
below:
ID Name DeptNo Sal Mgr Dependents

131 Ram 20 10000 134 Father, Mother, Sister
132 Kiran 20 7000 136 Wife, Son
133 Rajesh 20 5000 136 Wife
134 Padma 10 20000 Son, Daughter
135 Devi 30 3000 137 Father, Mother
136 Satish 20 6000 Father, Mother
137 V.V. Rao 30 10000 Wife, First Son, Second Son

Here, the dependents column has non-atomic values. To make the relation in INF, we have to
convert the non-atomic values into atomic values as follows:
ID Name DeptNo Sal Mgr Dependents

131 Ram 20 10000 134 Father
131 Ram 20 10000 134 Mother
131 Ram 20 10000 134 Sister
132 Kiran 20 7000 136 Wife
132 Kiran 20 7000 136 Son
133 Rajesh 20 5000 136 Wife
134 Padma 10 20000 Son
134 Padma 10 20000 Daughter
135 Devi 30 3000 137 Father
135 Defi 30 3000 137 Mother
136 Satish 20 6000 Father
137 V.V. Rao 30 10000 Wife
137 V.V. Rao 30 10000 First Son

137 V.V. Rao 30 10000 Second Son

The dependents column in the above table is having atomic values. Observe that for each
dependent the other employee details such as ID, Name, Dept No, Sal and Mgr are repeated and
will form as a repeating group. As per the definition of INF, the above relation is in INF.
However, it is best practice to remove the repeating groups in the table.
Repeating groups refers to any set of columns whose values are related and repeat in the table.
According to the rule of first normal form, the table should not have repeating groups of column
values.

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