POLYTECHNIC UNIVERSITY OF THE PHILIPPINESMabini Campus, Sta. Mesa, ManilaACCO 4023

Written Report in

CHAPTER 9:DATABASE MANAGEMENT

Prepared by:Billones, JoanneNishioka, Chikaze T.Revilla, Ma. Dainty V.Submitted to:Professor David Fua

Databases, Data, and Information

DATABASE is a collection of data organized in a manner that allows access, retrieval, and use of thatdata.Data is a collection of unprocessed items, which can include text, numbers, images, audio, andvideo.

Information is processed data; that is, it is organized, meaningful, and useful.

Database Management System (DBMS) - A software that allows users to:a. create a computerized database;b. add, modify, and delete data in the database;c. sort and retrieve data from the database; and d. create forms and reports from the data in the databaseDATA INTEGRITY organizations treat data as one of their more valuable assetsbecause data is used to generate information it identifies the quality of the data data integrity is very important because computers and people use information to make decisions and take actions. GARBAGE IN, GARBAGE OUT (GIGO) A computing phrase that points out the accuracy of a computers output depends on the accuracy of the input.QUALITIES OF VALUABLE INFORMATION ACCURATE- information is error free VERIFIABLE- information can be proven as correct or incorrect TIMELY - Timely information has an age suited to its use. ORGANIZED - information is arranged to suit the needs and requirements of the decision maker. ACCESIBLE - information is available when the decision maker needs it. USEFUL - information has meaning to the person who receives it. COST-EFFECTIVE - Information should give more value than its cost to produce THE HIERARCHY OF DATA CHARACTERS could be numbers, letters, space, punctuation marks and other symbols.

FIELD is a combination of one or more related characters or bytes and is the smallest unit of date a user accesses. Field name uniquely identifies each field

-Field size defines the maximum number of characters a field can contain

DATA TYPE specifies the kind of data a field can contain and how the field is used

Text (a.k.a) Alphanumeric)- letters numbers, or special characters Numeric (also called number)- numbers only AutoNumber- unique number automatically assigned by the DBMS to each added record Currency- dollar and cent amounts or numbers containing decimal values Date- month, day, year Memo- lengthy text entries Object- photo, audio, video, or a document created Attachment- document or image that is attached to the field

RECORD is a group of relate fields.

DATA FILE is a collection of related records stored on a storage medium such as a hard disk or optical disc. A database includes a group of related data files.

MAINTAINING DATAFILE MAINTENANCE refers to the procedures that keep data current.File Maintenance Procedures: Adding Records -Users add new records to a file when they obtain new data.Using the Student Maintenance Form, an admissions department clerk adds a new student record. After the clerk takes the photo with the digital camera and confirms the data is correct, he or she adds the record to the database file.

Modifying Records -Generally, users modify a record in a file for two reasons: 1) to correct inaccurate data, or 2) to update old data with new data.The admissions department clerk scans the student ID card to display the students record. After confirming that the correct student record is displayed, the clerk modifies the students address.

Deleting Records -When a record no longer is needed, a user deletes it from a file. Sometimes, the DBMS removes the record from the file immediately. Other times, the record is flagged, or marked, so the DBMS will not process it again.The admissions department clerk displays the students record on the screen. After the clerk verifies that the correct student record is displayed, he or she deletes the record. The DBMS flags the student record on disk by placing an asterisk in the first position of the record.

VALIDATING DATAValidation is the process of comparing data with a set of rules or values to find out if the data is correct.Many programs perform a validity check that analyzes data, either as you enter it or after you enter it, to help ensure that it is correct. A validity check is a software control over input of data to a computer system. Data is compared with the type of data properly included in each input field, thus reducing data entry errors.Types of Validity Checks: Alphabetic/Numeric check: An alphabetic check ensures that users enter only alphabetic data into a field. A numeric check ensures that users enter only numeric data into a field. Range check: A range check determines whether a number is within a specified range. Consistency check: A consistency check tests the data in two or more associated fields to ensure that the relationship is logical and their data is in the correct format. Completeness check: A completeness check verifies that a required field contains data. Check digit: A check digit is a number(s) or character(s) that is appended to or inserted in a primary key value. Other Checks: DBMSs that include hyperlink and attachment data types can perform validity checks on data entered in those fields.

FILE PROCESSING VS. DATABASESAlmost all application programs use the file processing approach, the database approach, or a combination of both approaches to store and manage data.FILE PROCESSING APPROACHThis approach uses the file processing systems. In a typical file processing system, each department or area within an organization has its own set of files. The records in one file may not relate to the records in any other file.In a school that uses the file processing approach, the computer used by a registration department clerk and the computers used by advisors each has its own set of files.

Weaknesses: Data Redundancy same fields are stored in multiple files. Isolated Data difficult to access or share data stored in separate files in different departments.

DATABASE APPROACHThis approach uses the Database Management System.When an organization uses the database approach, many programs and users share the data in the database. The database does secure its data, however, so that only authorized users can access certain data items. While a user is working with the database, the DBMS resides in the memory of the computer.In a school that uses a database, the computer used by a registration department clerk and the computers used by advisors access data in a single database through the DBMS.

STRENGTHS: Reduced Data Redundancy most data items are stored in only one file, which greatly reduces duplicate data. Improved Data Integrity when users modify data in the database, they make changes to one file instead of multiple files. Thus, the database approach increases the datas integrity by reducing the possibility of introducing inconsistencies.

DISADVANTAGES OF DATABASES A database can be more complex than a file processing system. Requires people with special training to develop larger databases and their associated applications Databases require more memory, storage, and processing power than file processing systems. Data in a database can be more vulnerable than data in file processing systems. If the database is not operating properly or is damaged or destroyed, users may not be able to perform their jobs Unauthorized users potentially could gain access to a single database file that contains personal and confidential data.

Database Management SystemsDatabase Management System, or database program, is software that allows you to create, access, and manage a database. DBMSs are available for many sizes and types of computers. Whether designed for a small or large computer, most DBMSs perform common functions.COMMON FUNCTIONS OF DBMS Data DictionaryA data dictionary contains data about each file in the database and each field within those files. For each file, it stores details such as the file name, description, the files relationship to other files, and the number of records in the file. For each field, it stores details such as the field name, description, field type, field size, default value, validation rules, and the fields relationship to other fields.A sample data dictionary entry shows the fields in the Student file and the properties of the State field.

File Retrieval and MaintenanceA DBMS provides several tools that allow users and programs to retrieve and maintain data in the database. A query is a request for specific data from the database.Methods to Retrieve and Maintain DBSM Data1. Query Languages: A query language consists of simple, English-like statements that allow users to specify the data to display, print, or store.

2. Query by example: a feature that has a graphical user interface to assist users with retrieving data. One QBE technique is Filter by Form, which uses a form to show available fields. The database program retrieves records that match criteria you enter in the form fields.

3. Form: Sometimes called a data entry form, is a window on the screen that provides areas for entering or modifying data in a database. You use forms to retrieve and maintain the data in a database. When designing a form using a DBMS, you can make the form attractive and easy to use by incorporating color, shading, lines, boxes, and graphics; varying the fonts and font styles; and using other formatting features.4. Report Generator: Also called a report writer, allows users to design a report on the screen, retrieve data into the report design, and then display or print the report. Report generators usually allow you to format page numbers and dates; titles and column headings; subtotals and totals; and fonts, font sizes, color, and shading. Many allow you to include images, for example, a product catalog with photos and descriptions of products.This report, created in Microsoft Access, displays student information by major.

DATA SECURITY A DBMS: Provides means to ensure that only authorized user`s access data at permitted times. Allows different levels of access privileges to be identified for each field in the database. BACKUP AND RECOVERYA DBMS provides a variety of techniques to restore the database to a usable form in case it is damaged or destroyed.A backup, or copy, of the entire database should be made on a regular basis. Some DBMSs have their own built-in backup utilities. Others require users to purchase a separate backup utility, or use one included with the operating system.More complex DBMSs maintain a log, which is a listing of activities that change the contents of the database.DBMS that creates a log usually provides a recovery utility. A recovery utility uses the logs and/or backups to restore a database when it becomes damaged or destroyed.Continuous backup is a backup plan in which all data is backed up whenever a change is made.This backup technique can cost more than other backup strategies but is growing in popularity because of its benefits.

Relational, Object-Oriented, and Multi-dimensional DatabasesRelational DatabasesA relational database is a database that stores data in tables that consist of rows and columns.Each row has a primary key and each column has a unique name.A relational database uses terms different from a file processing system.A developer of a relational database refers to a file as a relation, a record as a tuple, and a field as an attribute. A user of a relational database, by contrast, refers to a file as a table, a record and as a field as a column.In addition to storing data, a relational database also stores data relationships. A relationship is a link within the data. In a relational database, you can set up a relationship between tables at any time. The tables must have a common column (field).

Varied terminologies for Relational Databases.

Structured Query Language (SQL) A popular query language that allows users to manage, update, and retrieve data. SQL has special keywords and rules that users include in SQL statements. Most relational database products for servers and mainframes include SQL. Many personal computer databases also include SQL.

Object-Oriented Databases An object-oriented database (OODB) stores data in objects. An object is an item that contains data, as well as the actions that read or process the data. A Student object, for example, might contain data about a student such as Student ID, First Name, Last Name, Address, and so on. It also could contain instructions about how to print a student transcript or the formula required to calculate a students grade point average. Object-oriented databases have several advantages compared with relational databases: they can store more types of data, access this data faster, and allow programmers to reuse objects. An object oriented database stores unstructured data more efficiently than a relational database. Unstructured data includes photos, video clips, audio clips, and documents. When users query an object-oriented database, the results often are displayed more quickly than the same query of a relational database. If an object already exists, programmers can reuse it instead of recreating a new object saving on program development time.Multidimensional Databases A multidimensional database stores data in dimensions. Whereas a relational database is a two-dimensional table, a multidimensional database can store more than two dimensions of data. These multiple dimensions allow users to access and analyze any view of the database data. A Webmaster at a retail business may want information about product sales and customer sales for each region spanning a given time. A manager at the same business may want information about product sales by department for each sales representative spanning a given time. A multidimensional database can consolidate this type of data from multiple dimensions at very high rates of speed. Nearly every multidimensional database has a dimension of time. The content of other dimensions varies depending on the subject. No standard query language exists for multidimensional databases. Each database uses its own language. Most are similar to SQL.Data Warehouses One application that typically uses multidimensional databases is a data warehouse. A data warehouse is a huge database that stores and manages the data required to analyze historical and current transactions. Through a data warehouse, managers and other users access transactions and summaries of transactions quickly and efficiently. A smaller version of a data warehouse is the data mart. A data mart contains a database that helps a specific group or department make decisions. Web Databases One of the more profound features of the Web is the vast amount of information it provides. The Web offers information about jobs, travel destinations, television programming, photos, movies, videos, local and national weather, sporting events, and legislative information. Some Web databases are collaborative databases, where users store and share photos, videos, recordings, and other personal media.

ACCESSING DATA IN A WEB DATABASETo access data in a Web database, you fill in a form or enter search text on a Web page. Many search engines such as Yahoo! use databases to store Web site descriptions. To access the database, you enter search text into the search engine.A Web database usually resides on a database server. A database server is a computer that stores and provides access to a database. In addition to accessing information, users provide information to Web databases. Many Web sites request users to enter personal information, such as name, address, telephone number, and preferences into an e-form (electronic form). The database then stores this personal information for future use. An organization, for example, may send e-mail messages to certain groups of customers.

Database Design Guidelines

Role of the Database Analysts and AdministratorsThe database analysts and administrators are responsible for managing and coordinating all database activities. The database analyst (DA) decides on the proper placement of fields, defines the relationships among data, and identifies users access privileges.The database administrator (DBA) requires a more technical inside view of the data. The DBA creates and maintains the data dictionary, manages security of the database, monitors the performance of the database, and checks backup and recovery procedures.

Role of the Employee as a UserEmployees should learn how to use the data in the database effectively. The amount of information available often amazes first-time database users. Instant access to information helps employees perform their jobs more effectively.