Consider Following Sales Invoice of Cool Company. 


The Fields in the original data table is as follows:

Zero Normal Form (UNF)

Data not normalized. 
SalesOrderNo, Date, CustomerNo, CustomerName, CustomerAdd, ClerkNo,
ClerkName, ItemNo, Description, Qty, UnitPrice

First Normal Form (1nf)

1. Separate Repeating columns into New Tables.
2. Create a new table containing the repeating data

The primary key of the new table (repeating group) is always a composite key;

  Sales Table 
  SalesOrderNo, ItemNo, Description, Qty, UnitPrice

Now remove repeating fields  from the original data table leaving the following.

 Customer Table
 SalesOrderNo, Date, CustomerNo, CustomerName, CustomerAdd, ClerkNo,
 ClerkName

Sales and Customer  tables in first normal form (1nf) now

What if we did not Normalize the Database to First Normal Form?

Repetition of Data will occur
The Sales order header data repeated for every line in sales order.

Another Example 

The Course and Student Table Created from data