What is a Primary Key?
Primary Key to a database table can be one or a combination of fields. The primary key serves as the unique identifier of each record in the table. This means that the primary key should be filled out for every record and there should not be any two records in the table with the exact same primary key. When performing table joins or value lookups, the primary key of the targeted lookup table must be present in the form of Foreign Key in the originating table.