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Conceptual Schema Describes the Meaning of Data in the Universe of Discourse Describes the Meaning of Data in the Universe of Discourse –Emphasizes on General, Conceptually Relevant, and Often Time Invariant Structural Aspects of the Universe of Discourse Excludes the Physical Organization and Access Aspects of the Data Excludes the Physical Organization and Access Aspects of the Data
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What is differences ?What is differences ?
Logical Data Independence Vs Logical Data Independence Vs Physical data independence ?Physical data independence ?
Conceptual SchemaConceptual Schema Describes the Meaning of Data in the Universe of Describes the Meaning of Data in the Universe of
Discourse Discourse – Emphasizes on General, Conceptually Relevant, and Often Emphasizes on General, Conceptually Relevant, and Often
Time Invariant Structural Aspects of the Universe of DiscourseTime Invariant Structural Aspects of the Universe of Discourse Excludes the Physical Organization and Access Aspects Excludes the Physical Organization and Access Aspects
of the Dataof the Data
Conceptual SchemaConceptual Schema
Another ExampleAnother Example
External SchemaExternal Schema Describes Parts of the Information in the Conceptual Schema Describes Parts of the Information in the Conceptual Schema
in a form Convenient to a Particular User Group’s Viewin a form Convenient to a Particular User Group’s View Derived from the Conceptual SchemaDerived from the Conceptual Schema
External SchemaExternal Schema
Another ExampleAnother Example
Internal SchemaInternal Schema Describes How the Information Described in the Conceptual Describes How the Information Described in the Conceptual
Schema is Physically Represented in a Database to Provide the Schema is Physically Represented in a Database to Provide the Overall Best PerformanceOverall Best Performance
Internal SchemaInternal Schema
Another ExampleAnother Example
Unified Example of Three SchemasUnified Example of Three Schemas
Building a Database SystemBuilding a Database System
Essentially the same as the process for building Essentially the same as the process for building any other information system, consists of three any other information system, consists of three basic phases:basic phases:
Requirements phaseRequirements phase: a data model is developed: a data model is developed Design phaseDesign phase: the data model is transformed into : the data model is transformed into
tables and relationshipstables and relationships Implementation phaseImplementation phase: create tables into the : create tables into the
DBMSDBMS
Requirement PhaseRequirement Phase
Data model is developedData model is developed A data model is a logical representation of the A data model is a logical representation of the
structure of the database structure of the database Its very important because design & Its very important because design &
implementation depend on this phaseimplementation depend on this phase– If the data model inaccurate, then the result will be If the data model inaccurate, then the result will be
waste, aggravation, delays and uselesswaste, aggravation, delays and useless
Example: Data ModelExample: Data Model
•Rectangular are entity & diamonds are relationships
•We will discuss this model in detail later…
The Design PhaseThe Design Phase
The data model transform into tables & The data model transform into tables & relationshipsrelationships
Data properties established Data properties established type, length, type, length, null/not null. null/not null.
Need for index determinedNeed for index determined Constraint, trigger, stored procedure are Constraint, trigger, stored procedure are
defineddefined Figure 1-19 KroenkeFigure 1-19 Kroenke
The Implementation PhaseThe Implementation Phase
Tables & relationships createdTables & relationships created– Via SQLVia SQL– Via Graphical design toolVia Graphical design tool
Stored procedure & trigger are written & Stored procedure & trigger are written & testedtested
Figure 1-20 KroenkeFigure 1-20 Kroenke
Application DevelopmentApplication Development Application development proceeds in Application development proceeds in
parallel with database developmentparallel with database development
Suggested structure of Report 1Suggested structure of Report 1 IntroductionIntroduction
– Brief overview of DBMS (name, vendor, Brief overview of DBMS (name, vendor, version, price (if any), primary user, history of version, price (if any), primary user, history of the DBMS, etc)the DBMS, etc)
– Description of DBMS features you want to Description of DBMS features you want to compare and why they are important.compare and why they are important.
Table comparationTable comparation AnalysisAnalysis ConclusionConclusion
