unit 5 organizing data and information. learning outcomes understand records in a database...
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Unit 5Organizing Data and Information
Learning OutcomesUnderstand records in a databaseUnderstand components of a DBMSIdentify database models and typesDefine
Database conceptsStructures & record keepingData languagesDevelopment toolsSecurity and admin
Principles of Information Systems, Eighth Edition 2
Data ManagementWithout data and the ability to process it, an
organization could not successfully complete most business activities
Data consists of raw factsTo transform data into useful information, it
must first be organized in a meaningful way
Principles of Information Systems, Eighth Edition 3
The Hierarchy of DataCharacter: a group of 8bits forming a byte
Can be an uppercase letter, lowercase letter, numeric digit, or special symbol
Field: group of characters, typically a name, number, or combination of characters that describes an aspect of a business object or activity
Record: collection of related data fieldsFile: collection of related recordsDatabase: collection of integrated and related
filesPrinciples of Information Systems, Eighth Edition 4
The Hierarchy of Data (continued)
5
Figure 5.1: The Hierarchy of Data
DefinitionsDatabase management system (DBMS):
group of tools that support database management and it’d performance in an organisation
Data independence: data is independent from the program that creates it. This means programs and data developed in for 1 app are compatible with programs and data from another app.
Data redundancy: duplication of data in separate files – can lead to inconsistency.
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Database Approach
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Keys*Key: field or set of fields in a record that is
used to identify the recordPrimary key: field or set of fields that
uniquely identifies the recordForeign Key: A non-primary key attribute in
the table that is a primary key in the other table.
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Data ViewsPhysical View:Physical View: Where is data stored physically?
Drive, disk, surface, track, sector, RecordTape, block, record number (key)Used by programmers
Logical View:Logical View: What data is needed? How do users need the data to be arranged?Organize factors into tables for application useProvide a way for tables to cross-reference
*
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Accessing File StructuresSequential file structure e.g. payroll
Data is stored and accessed in a sequence according to a key field
Good for periodic processing of a large volume of data, but updating with new transactions can be troublesome
Direct file structure e.g. reservationsData stored randomly and accessed directly using
an index of keys and related storage addresses.Indexed Sequential file structure
Records stored sequentially on direct access medium (e.g. hdd) with address for each record.
Index keeps track of addresses for speed. Sequential access for large amounts of data
O’BRIEN 10
Record ProcessingOnline vrs Batch
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DBMS Components1.1. Data dictionaryData dictionary:: Stores definitions of data elements, and data Stores definitions of data elements, and data
characteristics e.g. data type, amount of storage: txt 30characteristics e.g. data type, amount of storage: txt 302.2. Data LanguagesData Languages::
Data definition language: Data definition language: Specifies content and structure of Specifies content and structure of database and defines each data element e.g keys, relationship database and defines each data element e.g keys, relationship
Data manipulation language: Data manipulation language: allows users to access and allows users to access and change data and produce reports. E.g. SQL, QBEchange data and produce reports. E.g. SQL, QBE
3.3. Application Development ToolsApplication Development Tools: : Programs to develop apps to Programs to develop apps to use the database, e.g. CASE toolsuse the database, e.g. CASE tools
4.4. Software Security: Software Security: protect database from hacking & protect database from hacking & unauthorised access.unauthorised access.
5.5. Archiving, backup & recovery systems: Archiving, backup & recovery systems: in case database is in case database is lost/crashes, it can be recovered from backups or archives.lost/crashes, it can be recovered from backups or archives.
6.6. Report WritersReport Writers: : tools to specify a report format for retrieving datatools to specify a report format for retrieving data
Principles of Information Systems, Eighth Edition 12
Sample data dictionary report
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Structured Query Language (SQL)
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Examples of SQL Commands
Database Models1. Hierarchical2. Network3. Relational4. Multidimensional5. Object-oriented6. Object-relational
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Hierarchical Database ModelMay have more than one offspring, but only one parentTreelikeOne-to-many relationshipUsed for structured, routine types of transaction processing
Laudon 16
Network database modelMore complexMany-to-many relationshipMore flexible but doesn’t support ad hoc
requests well
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Relational Database ModelData elements stored in simple tablesCan link data elements from various tablesVery supportive of ad hoc requests but slower
at processing large amounts of data than hierarchical or network models
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The Relational Database Model
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The Relational Database Model (continued)
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The Relational Database Model (continued)
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Multidimensional DB modelA variation of
the relational model
Cubes of data and cubes within cubes
Popular for online analytical processing (OLAP) applications
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Object-oriented DB ModelData descriptions &
procedures that act on data are grouped together.
Key technology of multimedia web-based applications
Good for complex, high-volume applications
Can store more data types
Objects can be reused Faster data accessed
Principles of Information Systems, Eighth Edition 23
Object-Relational DB ModelCombines features of object-oriented and
relational databasesStandard relational database with facilities
for new data types (e.g. video) and operations to be added.
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Types of Databases1. Operational DB – to support business
operations2. Analytical BD – Summarized data 4
analysis3. Data Warehouse*4. Distributed - data may be spread across
several smaller databases in different locations .
5. End-user –developed by managers and other users on their own PCs
6. External/on-line – pay for access to external statistical online databases
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Data Warehouses, Data Marts, and Data MiningData warehouse: Logical collection of data
gathered from many operational DBs to support business and decision making.
Data mart: subset of a data warehouseData mining: automated discovery of
patterns, trends and rules from data in data warehouse to predict business strategy.
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Data Warehouses, Data Marts, and Data Mining (continued)
Principles of Information Systems, Eighth Edition 27
Figure 5.17: Elements of a Data Warehouse
Advantages of DBMSs
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Data sharingReduced data redundancy (no duplicates)Improved data consistency (more integrity)Data independence (data independent of the
application using it.)Improved data admin & control – better
overall protectionMore emphasis on data as a resource
Problems with DBMSs
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Concurrency problem – data used at same time - lock
Resource problems – costly initiallySecurity problems - cos data all in one place