Fundamentals of Databases

• Define data model


  An abstract model of which things to store and what information about them should be recorded.
• Define attribute


  A characteristic of an entity
• Name the three possible degrees of relationship between tables in a database

  One-to-one, one-to-many, many-to-many
• Define entity


  A thing about which data is to be stored
• What name is given to an attribute which can uniquely identify each attribute in a table

  Entity identifier / Primary key
• Why are databases normalised?

  So that they can be at their most efficient without any compromise to the integrity of their data
• What name is given to a primary key formed from multiple different attributes?

  Composite primary key
• What name is given to the new table created when forming a many-to-many relationship?

  Link table
• Which form of normalisation can be described as follows: All non-key attributes depend on the key, the whole key and nothing but the key?

  Third Normal Form (3NF)
• Which declarative language is used to query databases?

  SQL - Server Query Language
• Write a SQL statement to add the following information to the database Vehicles: Registration - RD63 0LE, Age - 5, YearManufactured - 2013


  INSERT INTO Vehicles VALUES (‘RD63 0LE’, 5, 2013)
• Which of the following commands would return all information from the database Vehicles?

  A - SELECT ALL FROM Vehicles

  B - FROM Vehicles SELECT EVERYTHING

  C - SELECT * FROM Vehicles

  C
• What is the role of a client-server database?

  To provide simultaneous access to a database for multiple clients
• What problem occurs when different users attempt to access the same field in a client-server database simultaneously?

  Concurrent access
• In which form of normalisation are partial key dependencies removed?

  2NF (Second Normal Form)
• Name three ways of managing concurrent access

  Three from:

  • Record locks
  • Serialisation
  • Timestamp ordering
  • Commitment ordering