Question

What are candidate key and composite key????​

Answer 1

Answer:

A candidate key is a unique key that can be used as a primary key. Composite key is a key of two or more attributes that uniquely identifies the row. A key is a set of columns that can be used to uniquely identify each row within a table.

Answer 2

Answer:

Candidate Key: The minimal set of attribute which can uniquely identify a tuple is known as candidate key. For Example, STUD_NO in STUDENT relation. The value of Candidate Key is unique and non-null for every tuple. ...

For Example, {STUD_NO, COURSE_NO} is a composite candidate key for relation STUDENT_COURSE.

Composite Key: A primary key having two or more attributes is called composite key. It is a combination of two or more columns.

An example can be − Here our composite key is OrderID and ProductID − {OrderID, ProductID}