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What are the differences between unique key and primary key? Get to know here!

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sam bawa
What are the differences between unique key and primary key? Get to know here!

Anyone that has been working with database management systems should have encountered terms like these- primary ley, unique key, so on and so forth. Although many know of the existence of these terms, many still struggle to define them. It is important to know the differences not just to work well in the field or with the programs and systems it is involved with, but also to answers questions regarding it during important tests or interviews. And, in general, it is worth it to know things such as these, in order to be more knowledge in a workplace or a learning environment. Many starts with what a primary and unique key is, then wonder about if there are any differences between the two and what purpose each of these keys serve. In order to clear up all those questions, down below, you will be able to figure out all the answers through an easy format of differentiation.

The most important difference is that its intended use varies from key to key. The biggest role of a primary key is to help identify a row within a table itself. There is a rather fancy term used for this called, entity integrity. It is by far the primary key’s most important task. In order for a table to be truly relational, the primary key needs to be well defined.

The unique key whereas allows a user to put additional conditions on columns, all of which are unique. By defining each column with the right sort of individual information, you are successfully segregating columns, at the same time linking it to the entirety of the database.

What is the difference between primary key and unique key?

  1. Definition

Before proceeding to further details, we should look at the definition of primary key and unique key.

  • Pimary Key

A primary key is an important part of database management system where it is used to identify every record in a table.

  • Unique Key

Unique key is a little similar to primary key. It is used to identify an individual tuple in a unique manner in any relation.

2. Number

Now that we have seen the definitions, let us the number of keys that are possible under the two.

  • Primary Key

In a table, only one primary key is possible.

  • Unique Key

On the contrary to primary key, in a table, there can be more than one unique key.

3. NULL Value

So far, we saw the easier concepts and some basic differences. Now let us delve a little more into the details of each of these terms. We will do this by starting off with the NULL value.

  • Primary Key

Primary keys cannot accept NULL value. This is default.

  • Unique Key

In unique keys, unlike primary keys, there can be one NULL value. However, ONLY ONE null value will be accepted by the code.

4. Clustered Index

Let us take a look at what kind of index each of those terms entail.

  • Primary Key

The index of a primary key is a clustered index. The RDBMA is organised in a physical fashion.

  • Unique Key

Unique keys have an index that is unique and non-clustered. This is by default.

One more important difference is:

  • In the datable, every table has the ability to have just a single primary key.

Hopefully, with the short and easy guide above, you know the definition of primary key and unique key, what they are used for and their differences from each other.

The importance of a data base in a company or business is sometimes highly understated. It is what will help the company derive necessary figures and numbers, ones that can bring about an important change in the outlook of the company. It can help turn a new leaf, increase profits and help in increasing the number of jobs you have to offer.

Learning the difference between a primary and unique key can go a long way in helping out. When in a workplace that has a database management system, you can deal with them and carry yourself better now that you have a little knowledge on the subject. It will help you understand sheets and codes better as well.

 

 

 

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