'Candidate key or Super key

Consider a relational table with different columns, what would you call the collection of unique and not null values, super key or candidate key?

sqldatabaserdbms


Solution 1:[1]

A Super key is a set or one of more columns to uniquely identify rows in a table.

Candidate keys are selected from the set of super keys, the only thing we take care while selecting candidate key is: It should not have any redundant attribute. That’s the reason they are also termed as minimal super key.

In Employee table there are Three Columns : Emp_Code,Emp_Number,Emp_Name

Super keys:

All of the following sets are able to uniquely identify rows of the employee table.

{Emp_Code}
{Emp_Number}
{Emp_Code, Emp_Number}
{Emp_Code, Emp_Name}
{Emp_Code, Emp_Number, Emp_Name}
{Emp_Number, Emp_Name}

Candidate Keys:

As I stated above, they are the minimal super keys with no redundant attributes.

{Emp_Code}
{Emp_Number}

As a Summary:

A Superkey is a set of columns that uniquely identifies a row.Whereas a Candidate key would be a MINIMAL set of columns that uniquely identifies a row. So essentially a Superkey is a Candidate key with extra unnecessary columns in it.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 philipxy

Related Questions