First Normal Form, or 1NF, is relatively straight forward. The idea behind it is that every attribute is atomic, that is, single valued, or, as it is often put, there are no repeating groups.
For example, if you have a customer table within your database you would not put orders in the customer table because each customer, hopfully, has more than one order.
| Name | Order No |
|---|---|
| Jones | 1 |
| Smith | 2 |
| Jones | 3 |
Obviously, there would be more data in the table. Probably columns for the customer address, phone number, perhaps customer number etc. But the point should be obvious. Jones has two orders, and so an order cannot be uniquely identified. If we select Jones we don’t know which order we are referring to. So the order numbers must be moved to another table. And doing that will bring the data into first normal form.