A database management system (DBMS) is a set of program that controls the creation, maintenance, and use of the database and its end users. Database management packages are available for micro, midrange, and mainframe computer systems. The four major uses of database management systems (DBMS) are discussed below.
Uses of database management systems
Database management packages (e.g. Microsoft Access) allow end-users to easily develop the databases they need. However, large organizations with client/server or mainframe-based systems usually place control of enterprise-wide data are development in the hands of database administrators (DBAs) and other database specialists.
This improves the integrity and security of organizational databases. Database developers use the data definition language (DDL) in database management systems to develop and specify the data contents, relationships, and structure of each database’s specifications.
Such information is cataloged and stored in a database of data definitions and specifications called the data dictionary, which is maintained by the DBA.
The Data Dictionary: A data dictionary is a computer-based catalog or directory containing meta-data, that about data. A data dictionary includes a software component to manage a database of data definitions, that is, meta-data about the structure, data elements, and other characteristics of databases.
For example, it contains the names and descriptions of all types of data records and their interrelationships, as well as information outlining requirements for end-users’ access, use of application programs, and database maintenance and security.
Data dictionaries can be accessed by the database administrator to report the status of any aspect of a firm’s meta-data. Some active data dictionaries automatically enforce standard data element definitions whenever end-users and application programs use a DBMS to access databases.
For example, an active data dictionary would not allow a data entry operator to enter the name of a customer that exceeds the defined size of that data element.
The database interrogation capability is a major benefit of a database management system. End-users can use a DBMS by asking for information from a database using a query language or a report generator.
The user can easily receive an immediate response in the form of video displays or printed reports. The query language feature lets the user easily obtain immediate responses to ad-hoc data requests: the users merely key in a few short inquiries. The report generator feature allows a user to quickly specify a report format for information.
SQL and QBE: SQL, or structured Query Language, is a query language found in many database management packages. The basic form of an SQL query is:
SELECT ………….. FROM ………. WHERE…………
After SELECT, list the data fields to be retrieved. After FROM, list the fields or tables form which the data must be retrieved. After WHERE specify conditions that limit the search to only those data records which are required.
For example, suppose a financial manager wants to retrieve the names, social security numbers, departments, and salaries of all employees who are financial analysts form the employee and payroll files in a human resources database. Then the user might use the SQL query to display such information.
Another query language in some database management packages is QBE or query by example. QBE’s point-and-click capabilities make it easier for end-users.
This method displays boxes for each of the data fields in one or more files. The user then uses a keyboard or mouse to fill in, click on, query, or checkboxes to indicate which information is wanted.
Graphical and Natural Queries: Most end users have difficulty correctly phrasing SQL and other database language queries. So most end database management packages offer GUI (graphical user interface) point-and-click methods, which are easier available that use natural language query statements similar to conversational English.
In general, the databases of an organization need to be updated continually to reflect new business transactions and other events. Other miscellaneous changes must also be made to ensure the accuracy of the data in the databases.
This database maintenance process is accomplished by transaction processing programs and other end-user application packages, with the support of the DBMS. End users and information specialists can also employ various utilities provided by a DBMS for database maintenance.
Application development processes can use the internal 4GL programming language and built-in software development tools provided by many DBMS packages to develop custom application programs. For example, one can use a DBMS to easily develop the data entry screens, forms, reports, or Web pages of a business application.
A DBMS also makes the job of application programmers easier, since they do not have to develop detailed data-handling procedures using a conventional programming language every time they with a program. Instead, programmers can include data manipulation language (DML) statements in the programs that cell on the DBMS to perform necessary data-handling activities.
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