Database notes

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Databases:

  • are persistent organised stores of related data on computer systems
  • they are organised so that computer programs can easily select or edit data items
  • persistent means that they are stored in secondary stroage so that they can be accessed later
  • handled by software
  • software has to be able to create, retrieve, update and delete data in a database. (C.R.U.D)
  • a serial file is a file of items one after another (takes too long to find a particular item)
  • a sequential file is a serial file in order (quicker to find particular items)
  • an indexed sequential file is a sequential file that is accessed using an index, which is a seperate file
  • a flat file database is a database consisting of only one table
  • a field is a characteristic of something stored on a database
  • a record is all the data about one item in a database
  • an entity is something that we store data about in a database
  • an attribute is a characteristic of an entity
  • data redundancy is the unnecessary repitition of data
  • data integrity is the state of data being as it should be, reflecting reality
  • validation is the process of checking data as it is input to ensure it is reasonable
  • verification is the process of checking that data is true or correct

Validation checks:

  • check digit- a calculation is performed on a number that generates another digit which is appended…

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