Database Systems Unit 16

What is a Database? Databases are everywhere! Student records Mobile phone call records Supermarket stock records Why use a database? Word Processors are used to process text Spreadsheets are used to process numbers What do databases process? What is data? Database Structure Presentation Unit 16

What is a Database A database is a collection of data Database Management Software (DBMS) is the application that creates and accesses the database Common DBMS include: Microsoft Access Oracle MySQL Databases store data in a structured way Database Structure Presentation Unit 16

Database Structure Databases are divided into tables so all the data about a certain thing (student, telephone call, stock item) is stored together Tables are further sub-divided into fields, which set the structure of a table by defining the data items to be stored Each table has a number of Records. Each record describes one ‘thing’ with values for each of the fields What are the benefits of storing data in a structure like this? Database Structure Presentation Unit 16

Primary Key One field within each table is normally chosen to be the primary key Unique identifier for each record Usually a numeric or alphanumeric code Ensures each record can be uniquely identified Additional keys can be defined to speed up searching for records in a large database Database Structure Presentation Unit 16

Database Objects Tables – store the data itself Queries – used to answer questions about the data. Can extract records which match certain criteria Reports – used to format the output of data from tables or queries in a user friendly way – mainly for printing. Forms – used to input and/or output data in a user friendly way – for on-screen use Database Structure Presentation Unit 16

Database Advantages Compared to a paper based filing system: Creating and inserting records is quicker You can sort the records in any order Records can be found quickly, searches can be done on any field Amendments can be easily done Space required is much less Data is more easily shared Compiling reports which draw data from many records is much easier Database Structure Presentation Unit 16

Database Advantages Compared to other software (e.g. Spreadsheet) Can create multiple related tables (not covered in this unit) Designed for large, multi-user databases Searches can be more complex and can be saved (queries) Can create reports and forms Can create complete end user applications Database Structure Presentation Unit 16

Database Disadvantages Database software can be quite expensive, complex to understand and difficult to learn how to use. Large multi-user databases require high performance hardware and expert technical support Databases need to be carefully designed in order to provide the required functionality and performance Care must be taken to ensure that the data that is put into the database is correct. If the database stores data about real people then it must be registered with the Data Protection Act and its requirements must be complied with. Database Structure Presentation Unit 16