When an organized collection of structured data or information is electronically stored in a computer system it is called a database. Usually, a database is controlled by a DBMS ( Database Management System). A database system is a combination of the data and the DBMS, and the applications associated with them. A database system is often shortened to just a database. For writing or querying data, most databases are known to use SQL (Structured Query Language) as well. Understanding things about databases can be a bit confusing. So, do you want to know about the attribute in database or about the types of attributes? If so, then stay and read this article.
1. What is Attribute in Database?Photo by luis gomes on Pexels
In general terms, an attribute in database is a describing property or characteristic in a relational database. It refers to a database component such as a table in a database management system (DBMS). It can also be called a database field. It’s used to describe the instances in the column of a database. It can define all items concerned with a certain category applied to all cells of a column. (See What are the benefits of studying computer science?)
2. What are Examples of Attributes?
The attribute in database is a describing property or characteristic. There can be many attributes in an entity. For example, students have many attributes like roll number, name, age, and the like. We use roll number as a unique identifier to identify the students as it is not repeated. To further understand this you need to understand the various types of attributes in database. (See What is System Unit in Computer?)
3. What are the Types of Attributes?
As you have already learned that the attribute in database is a characteristic or property of an entity and there can be any number of properties of an entity. Now, it is time to read about the types of attributes. These are the five types of attributes:
- Simple Attribute: When it’s not possible to further subdivide an attribute into components then it is a simple attribute. For example, the employee’s ID number, student’s roll number, etc.
- Single-Valued Attribute: It is an attribute that takes up only a single value for each entity instance. For example, we can take the age of an employee.
- Composite Attribute: When an attribute can be further split into components then it’s called a composite attribute. For example, your name can be split into first name, middle name, and last name, and an address can also be further split into house number, street number, state, city, country, and pin code.
- Multi-Valued Attribute: When an attribute takes up more than a single value for each entity instance, is called a multi-valued attribute. For example, the phone number of a student can be a landline or mobile.
- Derived Attribute: It can be derived from other attributes. For example, a student’s total and average marks.
- Complex Attribute: When there is the nesting of multi-valued and composite attributes then they form complex attributes. It’s not a very popular one as it’s rarely used in DBMS( DataBase Management System). For example, a person can have multiple emails, phone numbers, and an address. The phone number and email are multivalued attributes examples and the address is a composite attribute that can be further divided into state, city, street, and house number.
4. What is an Attribute in SQL Database?Image by Do Exploit from Pixabay
SQL stands for Structured Query Langauge and is a standard language for a relational database management system. In databases, it’s used for manipulating, sorting, and retrieving data. An attribute in SQL database system is used to describe the members of the entity. It can be used to describe a collection, a consolidated member, or a leaf member. (See Why Does Computer Hardware Fail?)
5. What is Attribute in DBMS? Give an Example
After understanding what is an attribute in database and attribute in SQL database, let’s explore attribute in DBMS. In general terms, an attribute in database is a characteristic or property of an entity in DBMS. It provides additional information about an entity which can have many attributes. One of such attributes of the entity is considered its primary key attribute.
In ER model in DBMS, an attribute can take its values from a set of possible values of each entity instance. For example, take an ER model diagram where the student is an entity. This entity has different attributes like Roll No, Age, Name, Phone Number, Date of Birth, Address, Street, City, State, Country, etc. Here the primary key of the student entity is Roll No as it is not repeated. To further broaden your knowledge about DBMS you will have to learn about the types of attributes in DBMS. (See Why Everyone Should Learn Programming?)
6. What is Attribute Type in DBMS?
There is an ER( Entity Relationship) model in DBMS which is used to generally describe data elements and study their relationship with the specified system. These data elements are referred to as entities. The entities have self-existence and are real-world objects. In DBMS these entities are represented in rectangle shapes. Attributes are used to define the properties and characteristics of these entities. There can be many attributes of an entity. You can learn about the attribute in database by understanding ita different types:
- Simple Attributes: They are independent attributes and are also known as atomic attributes cause they can’t be subdivided into other components and can’t be classified further. For example, if you take a student as an entity then the Roll No is its simple attribute as it can’t be subdivided further.
- Composite Attributes: Their functionality is the complete opposite of simple attributes as these attributes can be further subdivided into different sub-parts or components that form simple parts. Simply talking, composite attributes are made up of one or more simple attributes. For example, if you take a student as an entity then the address is a composite attribute. It can be subdivided into the country, state, city, street, landmark, etc. All these subdivided attributes are simple attributes.
- Single Valued Attributes: These attributes are those attributes that incorporate only a single value per entity instance. They cannot store more than one value. The value associated with single-valued attributes always stays the same. For example, the name of a person.
- Multi-Valued Attributes: These attributes function opposite of single-valued attributes. For an entity instance from a set of possible values, these attrites can store more value at a time. The co-centric elliptical shape is used to represent these attributes. For example, let’s again take a student as an entity where Roll_No and Age are single-valued attributes. It also has attributes like Email_id and Mobile_No which are multi-valued attributes. These attributes need to be multi-valued as in the real world student can provide more than one email id and phone number.
- Derived Attributes: The attributes whose values can be derived from other attributes are called derived attributes. These are always dependent on other attributes for their values. For example, for a student entity, the DOB attribute remains constant for the entity instance and is also a single-valued attribute. But from the DOB you can derive the age attribute which changes every year. With the DOB value, you can easily calculate the age of a person. Hence DOB is a single-valued attribute and age is a derived attribute dependent on it.
- Key Attributes: These attributes can uniquely identify an entity from an entity set and thus they act as the primary key of an entity. They are special types of attributes whose values must be non-repeating and unique. For example, for a student entity, the Roll_No attribute isn’t just a single-valued attribute and simple attribute but it is also a key valued attribute. It’s used to identify a student and is always unique.
- Stored Attributes: These attributes help in deriving the derived attributes. They have constant values that are fixed for an entity instance. For example, you can derive the age attribute for the DOB attribute. Here the DOB has a constant and fixed value throughout the entity’s life and thus it is a stored attribute.
- Complex Attributes: These are a combination of composite attributes and multi-valued forms of complex attributes. These values have many sub-sections in their values. You will rarely see the use of complex attributes in DBMS. For example, if you see an Address_EmPhone attribute then it represents the Address, Email, and Phone Number altogether. It’s a complex attribute made up of composite attributes like Address and multi-valued attributes like Phone No and Email.
7. Is Attribute a Column?
In a database, the principal storage units are called columns or attributes, or fields. Both attributes and columns are storage units but they are slightly different as the attributes are used to collect information related to an entity whereas the columns are used to collect information about a table. (See What is a 10-key experience and requirements?)
8. What is Simple Attribute in DBMS?
In DBMS, simple attributes are independent attributes that can’t be subdivided into other components and can’t be classified further. For example, if you take a student as an entity then the Roll No is its simple attribute as it can’t be subdivided further. Read about the 3 Types of Computer Language.
9. What is Key Attribute?Photo by Kevin Ku on Pexels
A key attribute in database can uniquely identify an entity from an entity set and thus they act as the primary key of an entity. They are special types of attributes whose values must be non-repeating and unique. For example, for a student entity, the Roll_No attribute is a key valued attribute. Check out What are the Categories of items Stored in Computer?
10. What is Tuple and Entity?
In DBMS, the data is mostly stored in a tabular format. The tables have rows and columns. A row is called a tuple in DBMS. On the other hand, an entity is a data element in DBMS. An entity has self-existence and is a real-world object. (See What are the benefits of learning Linux?)