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 table can contain many records, each of which can have many fields.
- 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
- Used to store structured data
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