Primary keys
The second aspect of a system's data model are its primary keys. Each of a system's Data tables can have zero or one columns designated as a primary key. For example, the key of an employees table might be employee_id.
A table's primary key column is its unique identifier column. Its rows should have unique values. NIM uses the primary key column to establish Intra-system relations and Relation items in Filters.
To get started, Assign primary keys to tables.