Week 5

• Databases


  A collection of data organised and structured in a way that allows for efficient storage, retrieval, and management of information
• Foreign key


  A non-unique key that appears in one table and matches the primary key of another table, used to link the two tables
• Tables in a relational model


  • Need to be connected by having matching data fields
  • Whenever the primary key in one table appears in another table, it becomes a foreign key to link up the two tables
  • Foreign key is a non-unique key (can have repeated values)
  • A foreign key is an attribute within one entity that uniquely identifies an instance (a record) of another entity
• Referential integrity


  • Every value of a foreign key must match a value of an existing primary key
  • Any Job_ID being added to the Lecturers entity must first exist in the Job_details entity