Relational Database Concepts

Question	Answer
Table	A data structure made up of rows and columns that contains data about the items and must have a unique name.
Record	A single row within a table. A collection of data about a single item or event. Made up of fields and can contain different data types. In a table, each record must be unique.
Field	An individual data item within a record. Should have a unique name and only contain a single data item. Have individual data types and can have their own validation.
Primary Key	A field in a table that allows each record to be uniquely identified. Every value of a primary key must be unique. Can be simple (1 field) or compound (2 or more fields).
Foreign Key	A field in one table that is linked to a primary key in another field.
Relationships	Links between tables. One-to-many Many-to-many One-to-one
Entity	The name given to anything you can store data about. E.g. CUSTOMER (Always written in capitals and single words) Each entity becomes a table.
Attribute	A characteristic of an entity. E.g. an attribute of the entity CUSTOMER would be 'surname'.
Duplicate data	Data that exists in two tables. (It is removed from a database through the process of normalisation and linking tables through relationships.)
Referential Integrity	Makes sure that for every record in a table with a foreign key, there is a record in the corresponding table with the primary key.

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	Created by Emma Dolby about 12 years ago