What is Key in DBMS?

Hello Friends,

In this blog post, I will let you know about one of the most important and interesting topics of a database that is KEY.

While reading the same subject or sometimes having relevancy with the technology you would have heard about this technical word key if not exactly the same then you would have heard like a primary key or foreign key.

So those who have been studying the database or have studied should know this technical word key and all further classification related to this word key.

Like its name key which is useful in opening a lock in our real life, it is used to find the particular tuple and attribute information in relation in DBMS.

In the database we have a table, in a table, we have several rows and column. Here key can be a particular column or attribute value which is used to identify whole row or tuple value.

A column which is made a key will have a unique value in all the row. On this basis, we can say that an attribute which uniquely identifies a tuple value is known as a key.

There are several types of keys in the database which are given below.


Candidate key: Unique tuple value for each attribute.
Primary key: uniquely identify a tuple, does allow null.
Foreign key: Help to access other table data.
Unique key: Uniquely identify tuple, allow null value.
Super key: composite key identify a tuple value. a minimal superkey is candidate key.
Alternate key: Uniquely identify the tuple value but not a primary key.

I will discuss each of these above-given keys one by one in detail in my upcoming blog.


You should be confused with a key in the database. it is simply a column which has a unique value in each row and on the basis of this value we fetch the detail of a particular row. We may fetch one or more row result with the help of this key and can show the result as per our requirement.

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Have a great time!