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Chapter 1Introduction to Oracle9i: SQL1 Chapter 1 Overview of Database Concepts

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  • Chapter 1Overview of Database Concepts

  • Database TerminologyDatabase logical structure to store dataDatabase Management System (DBMS) software used to create and interact with the database

  • Database ComponentsCharacterFieldRecordFile

  • Database Components - CharacterBasic unit of dataCan be a letter, number, or special symbol

  • Database Components - FieldA group of related charactersRepresents an attribute or characteristic of an entityCorresponds to a column in the physical database

  • Database Components - RecordA collection of fields for one specific entityCorresponds to a row in the physical database

  • Database Components - FileA group of records about the same type of entity

  • Components Example

  • Review of Database DesignSystems Development Life Cycle (SDLC)Entity-Relationship Model (E-R Model)Normalization

  • Systems Development Life Cycle (SDLC)Systems investigation understanding the problemSystems analysis understanding the solutionSystems design creating the logical and physical components

  • Systems Development Life Cycle (SDLC)Systems implementation placing completed system into operationSystems maintenance and review evaluating the implemented system

  • Entity-Relationship Model (E-R Model)Used to depict the relationship that exists among entities

  • E-R Model Symbols

  • RelationshipsThe following relationships can be included in an E-R Model:One-to-oneOne-to-manyMany-to-many

  • One-to-one RelationshipEach occurrence of data in one entity is represented by only one occurrence of data in the other entityExample: Each individual has just one Social Security Number (SSN) and each SSN is assigned to just one person

  • One-to-many RelationshipEach occurrence of data in one entity can be represented by many occurrences of the data in the other entityExample: A class has only one instructor, but each instructor can teach many classes

  • Many-to-many RelationshipData can have multiple occurrences in both entitiesExample: A student can take many classes and each class is composed of many studentsCan not be included in the physical database

  • Example E-R Model

  • NormalizationDetermines required tables and columns for each tableMulti-step processUsed to reduce or control data redundancy

  • Unnormalized Data Contains repeating groups in the Author column in the BOOKS table

  • First-Normal Form (1NF)Primary key is identifiedRepeating groups are eliminated

  • First-Normal Form (1NF) ISBN and Author columns together create a composite primary key

  • Composite Primary KeyMore than one column is required to uniquely identify a rowCan lead to partial dependency - a column is only dependent on a portion of the primary key

  • Second-Normal Form (2NF)Partial dependency must be eliminatedBreak the composite primary key into two parts, each part representing a separate table

  • Second-Normal Form (2NF)BOOKS table in 2NF

  • Third-Normal Form (3NF)Publisher contact name has been removed

  • Summary of Normalization Steps1NF: eliminate repeating groups, identify primary key2NF: table is in 1NF and partial dependencies eliminated3NF: table is in 2NF and transitive dependencies eliminated

  • Linking TablesOnce tables are normalized, make certain tables are linkedTables are linked through a common fieldA common field is usually a primary key in one table and a foreign key in the other table

  • JustLee Books DatabaseAssumptionsNo back orders or partial shipmentsOnly US addressesShipped orders are purged (deleted) at the end of the month

  • Structured Query Language (SQL)Data sublanguage Used to:Create or modify tablesAdd data to tablesEdit data in tablesRetrieve data from tables

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