Databases

• Structured data


  Any data that resides in a fixed field within a record or file so that it can be easily entered, stored, queried, and analysed
• Records


  Made up of fields
• Comma separated values (CSV)


  One method of storing a record
• CSV format

  1. Each record is put on its own line

  2. Each field is separated by a comma
• Pros of CSV

  • Very simple, text-based format
  • Can be read by many applications
  • Easy to use in programs
• Cons of CSV

  • Inefficient for large datasets
  • Can only store text data
  • No built-in means of sorting or searching
• Flat-file databases


  Used to store records of information in order to be searched or queried at a later date
• Flat-file database structure

  • Single table to store data about an 'entity'
  • Table stores data in fields (columns)
  • A record (row) is a complete set of fields put together
• Redundant data


  Data that is repeated in a database
• Primary key


  A field used to uniquely identify a specific row of data in a table
• Relational database


  A set of tables whose records are linked by certain fields
• Relational database structure

  • Each table contains data on one entity
  • Tables are linked by relationships using primary and foreign keys
• Foreign key


  When the primary key of one table is placed into another table
• Secondary key


  A key that may also be kept by the database, does not need to be unique