You are watching: The set of possible values for an attribute is a ____.
A real-civilization building of an entity form is dubbed an attribute. This is the features of an entity. It is stood for by an oval or ellipse in E-R diagram. Each attribute deserve to take only a collection of allowed worths. This is called the domain of that attribute. For example, we specify the roll_no of the ‘Student’ by a numeric value. So, the permitted values are just integers and also hence, ‘integer’ is the domain of attribute ‘roll_no’. Each attribute is represented by a separate column in a relational table.
For instance, The entity ‘Student’ has properties like Name, Address, Roll_no, Mobile_no, Age, DOB, Class, Section, and so on. So, when we make an E-R diagram then Name, Address, Roll_no, Mobile_no, Period, DOB, Section and also Class are represented as the qualities of the entity form ‘Student’.
In the above instance, we check out that we have actually supplied various modified oval symbols to recurrent the E-R diagram. Various icons reexisting miscellaneous kinds of the attribute. The text of one attribute(Roll_no) is underlined, the other attribute(Email) is composed in double oval, and so on We will certainly understand also all this as we go via this blog and also learn about assorted forms of characteristics and also exactly how they are stood for in the E-R diagram.
There are are many types of features which are as follows:Simple Attribute & Compowebsite AttributeSingle Valued Attribute & Multi-valued AttributeStored Attribute & Derived AttributeKey Attribute & Non-essential AttributeSimple Attribute & Compowebsite Attribute
This department is made on the basis that if the attribute have the right to be additionally divided or not right into more features. If it cannot be additionally divided it is a straightforward attribute and if deserve to be further divided it is a compowebsite attribute.Simple Attribute
A simple attribute consists of an atomic value which cannot be additionally separated. It is simply stood for by an oval. A easy attribute is straight linked to the entity form. While making the E-R diagram, we straight affix the oval through the rectangle.
For example, Roll_no of Student, Era of Student. It is represented in the E-R diagram as:
A Composite attribute deserve to be even more separated right into other characteristics. We represent this in E-R diagram by connecting an oval with oval i.e the composite attribute is likewise represented by oval and also the additionally split attribute all likewise stood for by ovals. When we convert this E-R diagram to the relational table then we don't have actually any type of column of the composite attribute. We have column only for the attribute which came after we better split the composite attribute.
For instance, Name of a student can be even more separated into initially name, middle name and also last name. The composite attribute name is also stood for by oval as well as the other attributes are additionally stood for by oval and also we connect the all the additionally separated qualities through the composite attribute. In the table, we will certainly have actually three columns i.e. First_name, Middle_name, and also Last_name. There is no such column called "Name".
Single Valued Attribute & Multi-valued Attribute
This department is made on the basis of exactly how many values have the right to be taken by the attribute. If the attribute can take more than one value, it is a multi-valued attribute. If the attribute takes just one value it is a single-valued attribute.Single-valued Attribute
This attribute has actually just one value. It is represented by a simple oval. Some simple attribute can likewise be a single-valued attribute. For instance, the Section of ‘Student’ is a simple attribute as it can’t be additionally divided. Also, it is a single-valued attribute bereason a student can't research in even more than one area.
For instance, Section of a Student.
This attribute has even more than one value. It is stood for by a dual oval. Some Composite keys have the right to likewise be a multivalued attribute. For instance, the deal with attribute of a student have the right to even more be separated right into ‘Locality’, ‘Town’ and ‘PIN’. So, we call it a composite attribute. Also, the resolve of a student deserve to have actually more than one value. A Student deserve to have actually more than one Address i.e Permanent Address and also Temporary Address. So, it can additionally be referred to as a multivalued attribute.
For example, A student can have actually even more than one e-mail resolve.
Stored Attribute & Derived Attribute
This classification is made on the basis that if the attribute is simply stored in the database or have the right to be derived from some other attribute.Stored Attribute
The worth of this attribute have to be gave by the user. This attribute is stored and can be provided for finding the value of various other features. It cannot be derived from any type of other attribute. It is also stood for by an oval. For Example, The Date of Birth of ‘Student’ has to be offered by the student.
Example: Date of Birth(DOB) of Student.
The value of this attribute is acquired from some other qualities. We know the value of some other attribute(stored attribute)and from stored attribute, we are deriving the worth of this attribute(derived attribute). This is done mainly bereason the worth for such attribute keeps on changing. It is represented by a damelted oval.
For example, The worth of age attribute is obtained from the DOB(date of birth) attribute.
Key Attribute & Non-crucial Attribute
This classification is made on the basis that if the attribute can uniquely recognize the entities or not. As the name argues crucial attribute will uniquely identify the entities whereas the non-essential features would not be able to uniquely determine the entities.Key Attribute
A vital attribute is used to uniquely determine the entities of an entity type. In a relational table, it represents the major vital of the table. It is represented by oval and the text in it is underlined. Even if all the various other characteristics of an entity are the same however the crucial attribute will certainly always be different.
Example: We have actually Roll_no as the crucial attribute of the ‘Student’ bereason 2 students deserve to never before has same roll number.
All the other attributes other than the key attribute are the non-essential characteristics. Two or even more entities can have the same value for this attribute. For instance, the Class attribute would certainly have actually the very same worth for all those students who are examining in the very same course.
Example: Class, Section, Age, Name and so on, are the non-crucial attributes.
Note: The very same attribute have the right to be of even more than one kind. For Example, The Address attribute is a composite attribute, multivalued attribute, stored attribute and a non-key attribute.
This is all around features. Hope you learned somepoint new now.
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