The entity set specifies the collection of all entities of a particular entity type in the database. An entity set is known as the set of all the entities which share the same properties. For example, a set of people, a set of students, a set of companies, etc. An entity set in the context of a database management system (DBMS) is a collection of similar types of entities. An entity, in this context, represents a real-world object or concept…
The 2-Tier architecture is the same as basic client-server. In the two-tier architecture, applications on the client end can directly communicate with the database at the server side. In a 2-tier architecture for a database management system (DBMS), there are two layers or tiers involved: the client tier and the server tier. Client Tier: This is where the user interface resides. It interacts directly with the end-user and sends requests to the server tier for processing. The client tier is…
What do you mean by extension and intension? Extension: The Extension is the number of tuples present in a table at any instance. It changes as the tuples are created, updated and destroyed. The actual data in the database change quite frequently. So, the data in the database at a particular moment in time is known as extension or database state or snapshot. It is time dependent. Intension: Intension is also known as Data Schema and defined as the description of the…
Data abstraction in DBMS is a process of hiding irrelevant details from users. Because database systems are made of complex data structures so, it makes accessible the user interaction with the database. For example: We know that most of the users prefer those systems which have a simple GUI that means no complex processing. So, to keep the user tuned and for making the access to the data easy, it is necessary to do data abstraction. In addition to it,…
An extension of an entity type is specified as a collection of entities of a particular entity type that are grouped into an entity set. In the context of a database management system (DBMS), an extension of an entity type refers to the instances or occurrences of that entity type. For example, if you have an entity type “Employee,” the extension of this entity type would be the actual employees in a company database, each representing a distinct instance of…
The 3-Tier architecture contains another layer between the client and server. Introduction of 3-tier architecture is for the ease of the users as it provides the GUI, which, make the system secure and much more accessible. In this architecture, the application on the client-end interacts with an application on the server which further communicates with the database system.
What is System R? How many of its two major subsystems? System R was designed and developed from 1974 to 1979 at IBM San Jose Research Centre. System R is the first implementation of SQL, which is the standard relational data query language, and it was also the first to demonstrate that RDBMS could provide better transaction processing performance. It is a prototype which is formed to show that it is possible to build a Relational System that can be…
DBMS is a collection of programs that facilitates users to create and maintain a database. In other words, DBMS provides us an interface or tool for performing different operations such as the creation of a database, inserting data into it, deleting data from it, updating the data, etc. DBMS is a software in which data is stored in a more secure way as compared to the file-based system. Using DBMS, we can overcome many problems such as- data redundancy, data…
Following are three levels of data abstraction: Physical level: It is the lowest level of abstraction. It describes how data are stored. Logical level: It is the next higher level of abstraction. It describes what data are stored in the database and what the relationship among those data is. View level: It is the highest level of data abstraction. It describes only part of the entire database. For example– User interacts with the system using the GUI and fill the…
An entity set that doesn’t have sufficient attributes to form a primary key is referred to as a weak entity set. The member of a weak entity set is known as a subordinate entity. Weak entity set does not have a primary key, but we need a mean to differentiate among all those entries in the entity set that depend on one particular strong entity set.