Which type of key Cannot be a primary key?

What Cannot be a primary key?

Primary key will not accept NULL values whereas Unique key can accept NULL values. A table can have only one primary key whereas there can be multiple unique key on a table. ... Comparison Chart:ParameterPRIMARY KEYUNIQUE KEYNumber of keys that can be defined in the tableOnly one primary keyMore than one unique key

Can a compound key be a primary key?

Composite Key Declaration When over one column or field in a table are combined to achieve the task of uniquely identifying row values, then that composite key can be either a primary or a candidate key of that table.

What are the types of primary key?

Types of keys:Primary key. It is the first key used to identify one and only one instance of an entity uniquely. ... Candidate key. A candidate key is an attribute or set of attributes that can uniquely identify a tuple. ... Super Key. ... Foreign key. ... Alternate key. ... Composite key. ... Artificial key.DBMS Keys: Primary, Foreign, Candidate and Super Key - javatpoint