First Normal Form Definition
Repeating groups of fields have been removed
Data is positional independent (columns do not contain database data: i.e. sales_2001, sales_2002
Each field (cell) contains only a single value
Every row in the table contains the same column names and data types as the previous row
A primary key has been defined
Each attribute field is linked to a primary key field (in our example below, Emp_Hire_Date is linked to key field Employee_Name and Project_Manager is linked to key field Project_Name)
A summary of this list above is often stated as 'All fields in the database are atomic', meaning they are reduce to a single data value in each cell of the table.
Example
The following table is in first normal form (1NF/1ST):
Project_Name (primary key field when combined with Employee_Name)
Employee_Name
Emp_Hire_Date
Project_Manager
Problems With Data Stored in 1NF
Data duplication: within the same project the project manager name will be duplicated. If the manager is replaced then all records for that project will need to be updated (cascade update related records). The result is more space is used for each record and processing time is consumed checking updates and performing updates.
To add a project manager you should already have an employee in the project.
See our 2nd
normal form table design discussion.
