Found 115 Articles for RDBMS

SQL (Structured Query Language) is a computer language which is used to interact with an RDBMS (Relational Database Management System). It is basically a method of managing, organizing, and retrieving data from a relation database. In SQL, two important concepts are used namely, function and procedure. A function calculates the results of a program based on the inputs provided, whereas a procedure is used to perform some tasks in a specific order. There are many other differences between functions and procedures, which we will discuss in this article. What is Function? A function, in the context of computer programming languages, ... Read More

A DBMS (Database Management System) is a software that is used to manage a database. It is used to create, update, delete and maintain a database and it provides controlled access to data. An RDBMS (Relational Database Management System) is a type of DBMS that is based on the relational model of data. It can be regarded as an enhanced version of DBMS. Read this tutorial to find out more about DBMS and RDBMS and how they are different from each other. What is a DBMS? DBMS stands for Database Management System. A DBMS stores data in the form of ... Read More

A data dictionary contains metadata i.e., data about the database. The data dictionary is very important as it contains information such as what is in the database, who is allowed to access it, where is the database physically stored etc. The users of the database normally don't interact with the data dictionary, it is only handled by the database administrators.The data dictionary in general contains information about the following −Names of all the database tables and their schemas.Details about all the tables in the database, such as their owners, their security constraints, when they were created etc.Physical information about the ... Read More

DBMS supports relational set operators as well. The major relational set operators are union, intersection and set difference. All of these can be implemented in DBMS using different queries. The relational set operators in detail using given example are as follows as follows − Student_Number Student_Name Student_Marks 1 John ... Read More

The different types of keys in DBMS are −Candidate Key - The candidate keys in a table are defined as the set of keys that is minimal and can uniquely identify any data row in the table.Primary Key - The primary key is selected from one of the candidate keys and becomes the identifying key of a table. It can uniquely identify any data row of the table.Super Key - Super Key is the superset of primary key. The super key contains a set of attributes, including the primary key, which can uniquely identify any data row in the table.Composite Key -  If ... Read More

A database contains a large amount of data. Not all of that data is user data, some of it can be metadata etc. So, it is very important that a database has data independence.Data independence basically means that if data is changed at a level, it does not impact the data view at the higher levels.Hence, the data at the higher levels should be independent of the data modification in the lower levels. There is two types of data independence. These are −Logical Data IndependenceLogical data is independent from how data is actually stored on the disk. So logical data independence ... Read More

The relational data model is the most famous data model and is used by the majority around the world.This is a simple but efficient data model and has the capability to handle data in the best possible manner.Tables are used to handle the data in the relational data model. An example of a table containing data about the Employees in a company is as follows −Emp_NumberEmp_NameEmp_DesignationEmp_AgeEmp_Salary1JackManager35500002TomTechnician25250003HenrySecretary5030000The table Employee has the following characteristics −Tuple- A row of the table is called a tuple. It stores the data details according to the table schema.Column- A column of the database represents the same ... Read More

ER model is used to represent real life scenarios as entities. The properties of these entities are their attributes in the ER diagram and their connections are shown in the form of relationships.Some examples of ER model are −Hospital ER ModelThis is an ER model of a Hospital. The entities are represented in rectangular boxes and are Patient, Tests and Doctor.Each of these entities have their respective attributes which are −Patients - ID(primary key), name, age, visit_dateTests- Name(primary key), date, resultDoctor- ID(primary key), name, specializationThe relationships between different entities are represented by a diamond shaped box.Company ER ModelThe entities in this ... Read More

Many to Many relationship implies multiple relationship between any two entities. An example of this is: A class has multiple students but a student also attends multiple classes. So this is a many to many relationship between the entities STUDENT and CLASS.It is complicated to manage a many to many relationship. We cannot mention all the classes a student attends or all the students in a class in one table. This would become extremely complicated and difficult to understand. So, we have used a joining table. This is demonstrated as follows −The Student table stores the details of individual students such ... Read More

Data definition commands are used to create, modify and remove database objects such as schemas, tables, views, indexes etc.Common Data Definition commands −CreateThe main use of create command is to create a new table in database. It has a predefined syntax in which we specify the columns and their respective data types.syntaxCREATE TABLE (  ,  ,  ,   );Example  Create a student table with columns student name and roll number.CREATE TABLE STUDENT (STUDENT_NAME VARCHAR(30), ROLL_NUMBER INT );AlterAn existing database object can be modified using the alter command. Alter command can do following changes to any ... Read More