This type of integrity is a major component of overall data integrity, and it ensures the following:
There are no duplicate records in a table.
The primary key exclusively identifies each record in a table.
Every primary key value is unique.
Primary key values are not null.
You began establishing table-level integrity when you defined a primary key for each table and ensured its enforcement by making absolutely certain that each primary key fully complied with the Elements of a Primary Key. In the next chapter, you'll enhance the table's integrity further as you establish field specifications for each field within the table.