Databases The Kingsway School

Database Systems Databases are programs which store information in a logical way. Databases have a structure which helps when you want to interrogate the database. Data is often organised into tables. A separate table will be created for each set of data that is to be stored. A database has three clear levels: Fields. This is one piece of information e.g. Surname. A field is made up of the data and the name of the field. Records. This is all of the information about one thing (entity) e.g. a pupils information at The Kingsway School. File. This is all the information about one subject. Key field. A database should have one field which is unique and allows a search which can only find one record e.g. Membership Number

Types of Data Alphanumeric (Text). This type of field can hold letters and any other keyboard character including numbers. Remember Telephone Number is a text field. Numeric (Number). This type of field can only hold numbers and is used if calculations need to be done e.g. > or<. Date. This type of field can store data as dates e.g. DoB. Boolean. This type of field can only have two answers. E.g. Yes/No or True/False. It would normally be for a question like MOT? You may be asked to to decide what type of field is required!

Example of Data Structure Secretaries use office software to prepare documents.You need to think about the following when designing a database: Field names Key field? Field Size and type Coding data. Tables are best planned in a grid like this one: Field nameTypeSizeComment Member NoNumber4Key field SurnameText15Few people have names longer than 15 ForenameText10As above DoBDate8Age changes Card IssuedBoolean1Yes or No Memb TypeText1Coded field only needs 1 letter

Length of Records Two types of storage: Fixed Length. A field is a certain size and regardless of whether the data uses all that space the space is used e.g Paul in Forename is only 4 bytes but if the field is 10 it will take 10 bytes of memory. This makes searching easier as the program knows where the record ends and starts but it wastes memory. Variable Length Records. Only the data is stored. A marker e.g. a comma separates each field. No space is wasted but it makes searching slower.

Internet Resource A database is a way of storing information on a computer, often storing millions of records. 1.Record structureRecord structure 2.Data captureData capture 3.Why we use databasesWhy we use databases 4.Why code data?Why code data? 5.Using an AND/OR queryUsing an AND/OR query 6.Who uses databases?Who uses databases? 7.Exam TipsExam Tips 8.GlossaryGlossary Databases and data capture