IMS1907 Database Systems
Summer Semester 2004/2005
Lecture 2
Relational DBMS Software An Overview of Microsoft Access
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Database applications are an intermediary between users and DBMSDBMS processes application requests against database– create definitions, write, read, update
Database Systems
Database Application
DBMS Database
Users
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Relational database systems are currently the most common used in industryAccess, SQL Server, Oracle, Ingres, DB2, Sybase, MySQL, Informix…Organises the database as groups of related tablesTables are organised by business ‘themes’– reflect practices and policies of organisation
Tables can be ‘joined’ to discover related information occurring across ‘themes’
Relational Database Systems
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Table– storage entity for a database– a grid made up of rows and columns– each row is a record– each column is a field– made up of records containing data about a ‘thing’
• customer, sale, rental, loan, supplier, product…– like a folder in a filing cabinet
Relational Database Terminology
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Record– unit within a table, normally a row of the table– contains related data about the entity
• a single transaction’s details, summary details,…– like a sheet of paper in a folder
Field– a smaller unit within a record, a column in the table– contains a single fact about the entity– like a field on a sheet of paper in a folder
Relational Database Terminology
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Keys– defined from one or more fields of a table– used to order, identify and retrieve data
Primary Key (PK)– a unique identifier for a particular record– no two records can share the same PK– often an ID number useful to a business
• customer number, student number, licence number,…
Relational Database Terminology
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Secondary Key – defined from one or more other fields of a a table – used to arrange database in some other order– can be multiple occurrences in a database
Foreign Key (FK)– one or more fields of a table that appear as a PK
in another table– can be multiple occurrences in a database– used to join tables based on common information
Relational Database Terminology
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Table Structure – metadata definitions– instructions regarding arrangement and format of
data in record– keys, data type, length– formats, masks, validation rules– constraints, rules
Relational Database Terminology
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Forms – alternative method to datasheet for entering and
accessing data– screen-based form appears similar to paper-based
equivalent of the record– can be used to both capture and display data– allow entry, editing, viewing and deletion of
records in one or more table
Relational Database Terminology
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Reports – provide the ability to arrange data from one or
more tables, and view and print the data for later use
– can also be used to perform calculations, summarise, and group information before viewing
– screen-based report can appear similar to paper-based equivalent of the report
– primarily a display mechanism only
Relational Database Terminology
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Queries – allow you to answer specific questions about data
in the database– can be used to display records based on criteria,
perform calculations, summarise information, sort and group information, or delete data from one or more tables in database
– can be regular or ad hoc
Relational Database Terminology
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Creating Access Tables - Design View
properties
data type
data description
Primary key
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Sorting TablesUnsorted data
Data sorted by Member_No
Sort filters
Field to sort on
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Relationships Between Tables
edit relationship
related fields
relationship