The First Normal Form (1NF)
Let us first describe 1NF:
Definition: A relation (table) is in 1NF if
1. There are no duplicate tuples or rows in the relation.
2. Every data value stored in the relation is one-valued
3. Entries in a column (attribute) are of the similar kind (type).
Please note that in a 1NF relation the order of the attributes (columns) and tuples (rows) does not matter.
The first necessity above means that the relation must have a key. The key may be one attribute or composite key. It may even, possibly, have all the columns. The first normal form describes only the basic structure of the relation and does not determine the anomalies.