Databases Session - Overview
• What is our starting point? Introductions! • Databases • Database Management System • Relational Databases • Query Methods • Problem areas for student learning. Databases – Definition
• “A database is a persistent organised store of data” • Persistent? – Data is retained even when the application is not in use. • Organised? – The data is logically structured to enable easy storage, retrieval and manipulation of information. • Store of data? – Granular level information, grouped together to describe an entity Databases - Definition
• A database does not have to be electronic. • An address book, that most people have, is a database. The book itself provides a structure to contain the information. • So formally the term database describes both the data and supporting data structures. Database Management Systems (DBMS)
• A database management system is a software package that DB manages access to a database. • Microsoft Access, Oracle, SQL Server, MySQL, and many new DBMS freebies on the Cloud! Database Management Systems (DBMS)
Database System • A database management system is a software package that DB manages access to a database. • Microsoft Access, Oracle, SQL Server, MySQL, and many new DBMS freebies on the Cloud! Database Management Systems (DBMS)
Application
SQL DBMS
DB
www Database Management Systems (DBMS)
• Your database is simply a holding place for your • Create data. It isn’t capable of doing anything other than that. • Read • The DBMS is what allows us to interact with the • Update database. It allows us to design, build and maintain the database • Delete and once built we can..... Relational Databases: Entities
• An entity is anything which can be uniquely described by a set of attributes (characteristics/properties) – E.g. A gallery, a painting, an artist, a supplier, an exhibition. – A gallery can be uniquely described by its name, address, postcode, telephone number etc. Therefore a gallery is an entity. – Think of attributes that may uniquely describe the other entities. • An entity is a concept Relational Databases: Tables
• A table is the physical form of an entity. • A field is the physical form of an attribute • E.g. A gallery is an entity which will have its own table where the details of particular galleries may be stored. Fields Name Address PostCode Telephone Mima Middlesbrough TS1 3BA 01642 123456 Tate Modern London L13 3RF 0845 123456 Baltic Gateshead NE14 1TH 0845 654321 Records
• The collection of data for each name constitutes a record • Within each record the information is held in fields
Organisation
Poor Example – too much repetition
Artist Name Artist DOB Artist Origin Painting Title Genre Date Andy Warhol 06/08/1928 USA Marilyn Pop Art 1961 Andy Warhol 07/08/1928 USA Eight Elvises Pop Art 1963 Andy Warhol 08/08/1928 USA Campbell's soup Pop Art 1962 Organisation
Better Example – but how are they linked?
Artist Name Artist DOB Artist Origin Andy Warhol 06/08/1928 USA
Painting Title Genre Date Marilyn Pop Art 1961 Eight Elvises Pop Art 1963 Campbell's soup Pop Art 1962 Organisation
Perfect Example – both tables linked using KEYS! Primary key Artist ID Artist Name Artist DOB Artist Origin
1 Andy Warhol 06/08/1928 USA
Painting Title Genre Date Artist ID
Marilyn Pop Art 1961 1 Foreign Key Eight Elvises Pop Art 1963 1
Campbell's soup Pop Art 1962 1 Relationships between tables
A gallery can display many paintings • A relational database allows tables with common Gallery information to be connected. 0..n • E.g An gallery displays paintings, and artists create THE paintings. DATA Painting • Rather than putting all the MODEL information into one table we can split it into 3 to 1..n avoid repetition of records • This organisation causes Artist confusion amongst students! An artist can create many paintings
Major Components of Database System
• Tables • The table structures will hold data on areas that are needed, eg galleries, artists and paintings. • Queries • There would be no point having tables of stored data if they cannot access it. A DBMS allows you to set up queries to pull out information, e.g. all artists born before 1850. Queries allow you to select, insert, update and delete data. • Reports • To give formalised output of information and can include data from more than one table, e.g. All artists exhibiting at Mima in January. Can also include summaries/processed calculations.
TIME FOR SOME EXAMPLES Resources
• This is a large subject, with some of the topics only touched upon here, but a full set of workbooks will accompany this workshop • Useful references... • Sample data models • Microsoft Dynamic Data • Zoho Creator • Mendix • Caspio • Microsoft Lightswitch • Any questions? • During the break please think about which areas you would like to explore further..... Take a break!