Hello Friends, In this blog post(What is Key in DBMS), I will let you know about one of the most important and interesting topics of a database that is KEY. What is key in DBMS?
While reading the same subject or sometimes having relevancy with the technology you would have heard about this technical word key(What is Key in DBMS) 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(What is Key in DBMS).
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 to DBMS|What is Key in DBMS|
In the database we have a table, in a table, we have several rows and columns. Here key(What is Key in DBMS) can be a particular column or attribute value that is used to identify a whole row or tuple value.
A column that is made a key will have a unique value in all the rows. On this basis, we can say that an attribute that uniquely identifies a tuple value is known as a key.
Within this blog post, we will explore What is key in the database? What is key in DBMS with an example? What are the keys? What are the candidate key and super key in DBMS? What is the Super key in DBMS, What is the primary key in DBMS,…
….What is the candidate key in DBMS, Super key in DBMS with an example, Unique key in DBMS, Alternate key in DBMS.
What is key in the database?
In relational database system keys plays an important role to create the relationship between one and more database tables or entity. Keys are also used to identify the database records uniquely with the help of key constraints.
There are various keys in the database system and some important keys are the candidate key, primary key, unique key, alternate key, and foreign key.
What is the Super key in DBMS?
The super key is a set of one and more attributes to uniquely identify the whole tuple records. The super key is a superset of candidate key and a super key may or may not be a candidate key. But each candidate key is a super key.
What is the primary key in DBMS?
The primary key is also a candidate key that uniquely identifies the tuple value without allowing a null value. Each database table can have only one primary key. Whereas there can be more than one candidate key in one database table.
What is the candidate key in DBMS?
Just like a primary key candidate key also identify the tuple value uniquely, but the candidate key can allow a null value. So a minimal set of attributes or columns that can identify the whole row records is considered as a candidate key. All key that has a property to identify the records uniquely is a candidate key.
Unique key in DBMS?
A unique key is also a candidate key, a set of an attribute that uniquely identifies the tuple value in a database table. A unique key can allow the null value to be inserted. There could be more than one unique key in one database table. A unique key forms a non-cluster index.
What is the clustered index and non-cluster index?
Cluster index: for example, you insert the records 2, 1, 5 then in the database it will be inserted like 1 2 5. This is a clustered index. Inside the clustered index, the records are arranged in order.
Non-cluster index: for example, you enter the records 1, 2, 5, 3 in the database they will be inserted with the same serial number as 1 2 5 3. This is called the non-cluster index. The order that you enter is the order shown in the database.
What is the Alternate key in DBMS?
The candidate key which is other than the primary key is considered as an alternate key. Suppose in a database table of students there are two candidate key student roll no. and student phone. In this case student roll no. will be the primary key of the table and the student phone will be an alternate 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(What is Key in DBMS) in the database. it is simply a column that 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 results with the help of this key and can show the result as per our requirement.
Using this blog post(What is Key in DBMS) we have discussed What is key in the database? What is key in DBMS with an example? What are the keys? What are the candidate key and super key in DBMS? What is the Super key in DBMS, What is the primary key in DBMS, What is the candidate key in DBMS, Super key in DBMS with the example, Unique key in DBMS, Alternate key in DBMS.
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