Database Management System Data Dictionary A database management system is a collection of programs that are used to create and provides maintain a Database Management. It is a general-purpose system that provides the following facilities:
- It provides the facility to define the structure of the database. The user can specify the data types, format, and constraints for the data to be stored in the database.
- It provides the facility to store data on a storage medium that is controlled by DBMS.
- It provides the facilities to insert, delete, update and retrieve specific data for reports.
Information word reference or vault contains information about each record in the database and each field in these documents. For each file, it stores the details such as file name, description, file’s relationship to other files and number of records in the file. For each field, it stores details about them. e than files such as field name, description, field type, field size, default value, validation rules and field’s relationship to other fields.
The data dictionary contains data about data. It is also known as metadata. It also contains data about programs and users. It can also store the details such as who accessed the data and when. DBMS utilizes information word reference for information approval checks since all subtle elements of approval checks are put away information lexicon.
Database Management lexicon can likewise be utilized to indicate a default esteem. A value initially displayed in thein a field is called default value. The user may use the displayed value or can change it and enter another value to store in the database.
File Maintenance and Retrieval:
- DBMS provides different tools to maintain and retrieve data in the Database Management.
Queries are used to retrieve the required data from the database. Data is retrieved by cats according to the criteria given by the user. The query is written in database access language. It retrieves data from the database and displays it in the form of a table. The most commonly used query language is SQL.
Suppose a table Students contains the following rows: The user executes a query to retrieve the records of the students who got more than 600 marks. The query will display the following table as result:
A query language provides simple statements to manipulate data in the database. The statements are English-like and are easy to use. It is very easy to learn without any programming background. Many DBMSs provide the facility of wizards to create a query.
Query by Example:
Dat Query by example (QBE) is used to retrieve data from the database without learning the query language. DBMSs provide a graphical user interface to assist the user in retrieving the data.
A graphical interface used to interact with the Database is called form. Forms are used to enter data into the database. A form consists of textboxes, labels, and buttons that are used by users for entering data easily. The user can also retrieve, change and update data by using the forms. A form of the send entered data across a network or the Internet is called electronic form or e-form. Some important advantages of forms are as follows:
- Forms are easy to use and user-friendly
- Forms use graphical interface that is attractive.
- The user can interact with the database without technical knowledge.
Reports are the outputs of the database application. The user can generate different tune of reports by manipulating the database. Reports are very important in making key decisions.
The information on the reports is arranged in different ways. A report may also contain graphs, charts, and tables etc. A part of DBMS that is used to create reports is known as report writer or report generator. Some important advantages of reports are as follows:
- Reports provide a quick result from databases.
- Reports help in making important decisions.
- Reports can display processed data using graphs and charts etc.
- Reports can be printed or emailed easily.