Chapter 10 Managing a Database

Database is a collection of data organized in a manner that allows access, retrieval, and use of that data.
Data is a collection of unprocessed item for example text , number , images , audio and video
Information is processed data

Database , Data and Information 

• Database software as we called a database management system (DBMS) it allow user to -create a computerized database                                                   -add,modify and delete data                                                         -sort and retrieve data                                                                   -create forms and reports from the                                                 data 
• Data integrity identifies the quality of the data 
• Garbage in ,garbage out(GIGO) points out the accuracy of a computer output depends on the accuracy of the input
• For information should have the following characteristic that is accurate , verifiable,timely,organized,accessible,useful andcost-effective

The Hierarchy of Data

• a character is one byte for the number , letters ,space punctuation marks or other symbols
• a field is a combination of one or more related characters for example field name , field size and data type
• common data types include text , numeric , AutoNumber , currency , date , memo , yes/no , hyperlink , object and attachment
• a record is a group of related fields-a primartkey uniquely identifies each record 
• a data file is a collection of related record

Maintaining Data

• File maintenance refers to the procedures that keep data current -adding records,modifying records and deleting records
• users add new records to a file when they obtain new data
• user modify a record to correct inaccurate data or update olad data
• Validation compares data with a set of rules or values to find out if the data is correct -alphabetic/numeric check ,range check , consistency check , completeness check , check digit and other checks

File processing Versus Databases 
File processing system

• each department has its own set of files 
• used for many years
• have data redundancy 
• isolate data

Database approach

• programs and users share data 
• reduce data redundancy
• improve data integrity 
• share data
• allows easier access
• reduces development time 
• can be more vulnerable

Database Management Systems

• a data dictionary contains data about each file in the database and each field in those files
• a DBMS provides several tools that allow user and programs to retrieve and maintain data in the database 
• a query language consists of simple , English -like statements that allow users to specify the data to display, print, or store
• query by example (QBE) provides a GUI to assist users with retrieving data
• A dorm is a window on the screen that provides areas for entering or modifying data in a database
• a report generator allows users to design a report on the screen , retrieve data into the report design , and then display or print the report
• A DMS provides means to ensure that only authorized users access data at permitted times - access privileges                                                                          -principle of least privilege
• A DMBS provides a variety of techniques to restore the database to a usable form in case it is damaged or destroyed         -backup          -log       -recovery utility     -continuous backup

Relational, object-Oriented, and multidimensional Databases

• a data model consists of rules and standards that define how the database organizes data
• A relational database stores data in tables that consist of row and columns .each row has a primary key and each column has a unique name
• 
  
• a relationship is a link within the data 
• structured query language (SQL) is a query language that allows users to manage, update,and retrieve data
• an object-oriented database (OODB) stores data in objects 
• examples of applications appropriate for an object-oriented database include multimedia database , groupware database , computer aided design database and hypertext database
• a multidimensional database can store data in more than two dimensions of data
• a data warehouse is a huge database that stores and manages the data required to analyze historical and current transactions

Wed Databases

• databases on the web allow you to

   -shop for products or                                                                              services

   -buy or sell stocks 

   -search for a job

   -make airline reservations

   -register for college classes

   -check semester grades

Database Administration 

• it is important have have a carefully designed database
• Database Analyst(DA)-decides on proper filed placement,defines data relationship ,and identifies users access privileges
• Database Administrator (DBA)-creates and maintains the data dictionary ,manages security , monitors performance and checks backup and recovery procedures
• Employees shold learn how to use the data in the database effectively-interact with database                                                                  -identify new data for the database                                              -maintain the database