Discuss the difference between the ER model and Relational Model?

E-R Model and Relational Model both are the types of Data Model. Data Model describes a way to design database at physical, logical and view level. The main difference between E-R Model and Relational Model is that E-R Model is entityspecific, and Relational Model is table specific. Let us discuss some differences between E-R Model and Relation model with the help of comparison chart shown below.

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Define the following terms: Entity, Attribute, Attribute Value, Relationship Instance, Composite Attribute, Multi-valued Attribute, Derived Attribute, Complex Attribute, Key Attribute, Value set(Domain), Recursive Relationships?

Entity – An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity. Attribute – In general, an attribute is a characteristic. In a database management system (DBMS), an attribute refers to a database component, such as a table. It also may refer to a database field. Attributes describe the instances in the row of a database. Attribute Value – Attribute value is the real data of a particular entity for each of its attributes. In other word, associated with each real world entities are certain attributes that describe that entity; value of these attributes for any entity is called attribute value. For example, attribute value of first_name of attribute of student_name can be Gyanendra. Relationship Instance – Each relationship instance ri...

Explain the four actors on the scene of Database?

For a small personal database, one person defines, constructs and manipulates the database . For a large organization, many people are involved in the design, use and maintenance of the large database Two types of actors of DBMS: 1. Actors on the Scene (day-to-day use of large database ) 2. Workers behind the Scene ( work to maintain database environment and are not involved in its contents ) Actors on the Scene Database administrators (DBA) are responsible for:  Authorizing access to the database  Coordinating and monitoring its use  Acquiring software and hardware resources Database designers are responsible for:  Identifying the data to be stored  Choosing appropriate structures to represent and store this data . End users - People whose jobs require access to the database.  Types of End Users • Casual end users • Naive or p...

Compare the difference between the following:

i) Entities and Attributes – Entity - An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity. ii) an attribute is a characteristic. In a database management system (DBMS), an attribute refers to a database component, such as a table. It also may refer to a database field. Attributes describe the instances in the row of a database. ii) Composite and Atomic attributes – Composite attribute − Composite attributes are made of more than one simple attribute. For example, a student's complete name may have first_name and last_name. Simple attribute (Atomic) − Simple attributes are atomic values, which cannot be divided further. For example, a student's phone number is an atomic value of 10 digits. iii) Single valued and Mu...

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