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AS Level Databases

Chapter 5

anika rajdev

on 6 January 2011

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Transcript of AS Level Databases

Relational Database Concepts
Chapter 5 Database Terminology Tables Records Fields Keys Composite Primary Key Foreign Key Secondary Key Contains data about items Made up of records and fields Must have a unique name Single row within the table Collection of data about a single item or event Individual items of data in a record Fields can be validated individually Fields are also called attributes Primary Key is a unique identifier for the record Where two or more fields are joined to make a unique indentifier for the record Primary Key in one table, but a normal field in another table Used to index a field Relationships One to One One To Many Many to Many when one record is linked to another record in another table when one record in a table is linked to many records in another table many links between two tables Referential Integrity Making sure that every record in a table corresponds with a primary key and foreign key Data Types Text/String Integer Real Boolean Date/Time Either one value or another anything that doesn't require calculations Numbers with decimal places Dates and Times whole numbers NOT telephone number 1901 847932894.902732 Good/Bad Wilmington 25/12/1992 Data Dictionary describes the structure and attributes of the data "items" to be used within the database Parameter Simple Complex Static Dynamic Where there is only one parameter e.g. all students who play basketball a query with more than one search parameters e.g. Year 12s AND play sport e.g. Year 13s OR do biology parameter is hard coded into the query the user has to fill in what they want to search, therfore a search box will pop up to ask you what you want to search
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