The primary key is part of the Table definition. There is one primary key is allowed for each table. And the columns contained in a primary key cannot have null values.
The primary key in DB2
A primary key constraint forbids duplicate values in one or more columns. A table with a primary key will be considered the parent table to a table with a foreign key, which becomes the dependent table.
- Primary must be defined while creating Table
- Only one Primary key is allowed
- The primary key column must not allow null values
Note: A nullable column cannot be a part of a primary key.