Composite key: Composite key vs Super key?|What is a composite key?| composite vs super?

Within this blog post we are going to let you know about the Composite key: Composite key vs Super key. A composite key is the combination of one and more attribute which can uniquely identify a tuple value.

For example: if a student relation has attribute student id, student name, student class, student project id. The data of this relation is given below|Composite key: Composite key vs Super key|

Inside this blog post(Composite key: Composite key vs Super key), we are going to cover What is a composite key gives an example? How do you define a composite key? What is the difference between a primary key and a composite key? What is a composite foreign key? Are Composite Keys bad? What is the composite key in the database? What is the composite key in SQL? Is a composite key a primary key?

What is a composite key to giving an example?

When the primary key has two or more attributes to identify the tuple values uniquely then this key is called a composite key.

How do you define a composite key?

When two or more columns are taken together to identify the whole records of a row then it is considered as a composite key. The combination of these attributes must identify the row records uniquely whereas composite key attributes may or may not identify the records uniquely.

What is the difference between a primary key and a composite key?

The primary key is the single column in the table which is capable to identify the whole records uniquely. The primary key value can never be null and we can not either modify or update the primary key value. Whereas the composite key is just like a candidate key where two or more columns uniquely identify the whole tuple value.

Table: Student

student idstudent namestudent classstudent project id
1Ravi9th101
2Rita9th102
1Shyam10th103
3Anil11th101

Here in the above table we can don’t have any unique column or candidate key which can uniquely identify the tuple value so, here we need to join two column value or attribute value to make a key which can easily identify the tuple in the above-given relation. So, we make student id and student as the primary key of this table, and this primary key is also known as a composite key of this table.

What is the difference between the composite key and the super key?

If you will see the definition of a super key which says that the combination of one and more attributes uniquely identifies a tuple value is called a super key you will confuse it with the composite key definition which is just looking similar at one glance.

But it is not like this, there is a difference between the composite key and super key. In the super key, the combination attributes have at least one candidate key which could be a primary as well as a unique key. But when we don’t have a candidate key in our table then we have to make a set of combine attribute which can easily identify a tuple uniquely. And now this combined key is called a composite key.

A candidate key is also known as minimal super key but in case of the composite key, there is no candidate key in the table.

Conclusion:

When we are in a situation where we are unable to identify a tuple value uniquely with the help of one single column or we don’t have a candidate key or primary key in our table then we need to combine more than one attribute or column to make a primary key which can fetch thee tuple result, this type of primary key is known as a composite key. We can say that the super key is also a composite key but there is some minor difference between them|Composite key: Composite key vs Super key|

Within this blog(Composite key: Composite key vs Super key), we have gone through What is a composite key give an example? How do you define a composite key? What is the difference between a primary key and a composite key? What is a composite foreign key? Are Composite Keys bad? What is the composite key in the database? What is the composite key in SQL? Is a composite key a primary key? A composite key example, Composite key in SQL, When to use a composite primary key.

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Anurag

I am a blogger by passion, a software engineer by profession, a singer by consideration and rest of things that I do is for my destination.