Databases

  • Created by: holly6901
  • Created on: 02-05-19 10:20
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  • Databases
    • Used to store structured data
      • Structured data is stored undr pre-defined headings
    • Data is said to be unstructured if it isn’t recorded in a pre-defined, organised way.
    • Data about one person is stored in a record (records are rows)
      • Each individual piece of data is stored in a field. (fields are columns)
    • Record structure
      • Before setting up a database, the record structure must be decided to create a structure suitable for the type of data to be stored and to ensure that data will be useful.
      • To create a database you need to answer the two questions.What information is needed?What validation could there be?
      • it is important to choose the correct field type for each field. This ensures that the data stored is usable and it makes validation easier.
      • The key field is a unique identifier for each record.
    • Storing data
      • a table can contain many records, each of which can have many fields.
        • A database also stores forms to enter data, reports to display data, and queriesto ask questions of the data, which can then be displayed in a form or a report.
      • A database in which all the data is stored in a single table is known as a flat file database.
    • A relational database has more than one table and the tables are linked using key fields.
      • When a primary key is used in another table it is called a foreign key.
    • The link between different tables is called a relationship. There are three possible relationships: one to one, one to many, many to many

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