Relational Model Constraints Constraints are restrictions on the values stored in a database based on the requirements. For example, in the relation EMPLOYEE, the Employee_ID must be a 4-digit number, the Date_of_Birth must be such that the age of employee should be >= 18 and <=65. Following are the various types of constraints in Relational Model:   Domain Constraint–It specifies that the value of every attribute in each tuple must...

  Relational Database Various types of databases were developed. One of them was relational database which was developed by E.F Codd at IBM in 1970. It is a collection of data items organized as a collection of relations where each relation corresponds to a table of values. A table consists of rows and columns. Each row in the table corresponds to a unique instance of data and each column is used...

  Database Management System (DBMS) A database management system is a collection of programs that enables users to create, maintain and use a database.It can be viewed as a repository of data that is defined once and then accessed by different users as per their requirements. In the Database approach,there is a single repository of data which is accessed by all the application programs as shown in the example below: The...

  Need for a Database In Traditional file processing, data is stored in the form of files. A number of application programs are written by programmer’s to insert, delete, modifyand retrieve data from these files. New application programs will be added to the system as the need arises. For example, consider the Sales and Payroll departments of a company. One user will maintain information about all the salespersons in the Sales...

  Introduction Data is a collection of raw facts which have not been processed to reveal its meaning. For example, test marks of every student in a school. Information is produced by processing data as shown in Figure1. For example, given the data of the test marks of all the students in a class, the average marks of all the students and the maximum and minimum marks in the class can...