Difference between primary key candidate key and super key?

Answer 1

A primary Key which uniquely identifies a row of table,primary key does not allow null values and also not allow duplicate values.

Superkey is defined in the relational model of database organization as a set of attributes of a relation variable (relvar) for which it holds that in all relations assigned to that variable there are no two distinct tuples (rows) that have the same values for the attributes in this set. Equivalently a superkey can also be defined as a set of attributes of a relvar upon which all attributes of the relvar are functionally dependent. If you more information so you can visit this website:http://www.iyogibusiness.com

Answer 2

Different set of attributes which are able to identify any row in the database is known as super key. And minimal super key is termed as candidate key i.e. among set of super keys one with minimum number of attributes. Primary key could be any key which is able to identify a specific row in database in a unique manner.

Answer 3

primary key. is a single field or combination of fields that uniquely defines a record. None of the fields that are part of the primary key can contain a null value. A table can have only one primary key while

A composite key is a primary key that consists of more than one column.Oracle will create a composite primary key index on the table to implement and enforce the composite key. Composite keys are also known as concatenated or aggregate keys.

ExampleFor example, the LINE_ITEMS table may have a composite key on {order_ID, item_Number}: CREATE TABLE line_items ( order_ID NUMBER, item_Number NUMBER, product_Id NUMBER, quantity NUMBER, PRIMARY KEY (order_ID, item_Number));