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Database and Information Management Chapter 9 – Computers: Understanding Technology, 3 rd edition
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Definitions Database - computerized system for storing information so that information can be searched for and retrieved when needed Entity – person, place, thing, or event Field – smallest data category in a database, generally has 3 attributes – data type, name, size (number of characters that can be entered) Record – collection of fields describing an entity Table – collection of records containing the same fields Primary key – For a field to be a primary key in a table, it must have a value for every record and the value must be unique (no 2 records with same value)
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Queries Queries – questions to retrieve needed information from database Structured Query Language (SQL) is the most popular database query language Example: SELECT Student.FName, Student.LName, Student.StuID FROM StudentData WHERE Student.GPA>3.49 AND Student.Enrolled=“YES”
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Databases Classified by Data Model Flat File Databases – contain only one table or file Relational Databases – information stored in tables related to each other so that a piece of data is stored in only one place Object-oriented Databases – data stored in objects – each object will have allowable actions (methods) associated with it
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Databases Classified by Function Operational databases – working systems that are continually being updated Data warehouse – Data is extracted from the warehouse but the warehouse is typically not modified or updated with new information
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Planning for a New Database Organizational structure for the data – what fields, grouping fields by table, choosing data types for fields Design a front-end user interface for the database for data entry Design reporting capabilities
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Database Objects Forms – Templates which facilitate entry of data into database Reports – Formatted output from database –Data filters – report will only show some records (e.g. WHERE clause in SELECT statement) Although form and report capabilities are part of databases, increasingly web-based forms and reports are being used for the “front end” leaving the database to do the “back end”
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Database Administrator Data loss or corruption Backup and recovery Database response time Record locking – simultaneous viewing is OK, but simultaneous editing is not Data Integrity – normalization aims to eliminate data redundancy Data validation – range checks, alphanumeric checks, consistency checks, completeness checks, referential integrity
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Database Operations Adding records Modifying records Deleting records Sorting records Indexing records – index makes retrieval quicker
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