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NORMALISATION

Beschreibung

A level A Level ICT Mindmap am NORMALISATION, erstellt von Fiona Faulkner am 14/05/2013.
Fiona Faulkner
Mindmap von Fiona Faulkner, aktualisiert more than 1 year ago
Fiona Faulkner
Erstellt von Fiona Faulkner vor mehr als 13 Jahre
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Zusammenfassung der Ressource

NORMALISATION
  1. 1NF
    1. All data is atomic
      1. Has a PK
        1. No repeating data/fields
          1. unique field names
          2. 2NF
            1. Already in 1NF
              1. All non-key fields are dependent on the whole PK
                1. all field data can be found by looking at entire PK
              2. 3NF
                1. table is already in 2NF
                  1. No functional dependency between non-key fields
                  2. ADVANTAGES
                    1. increased data integrity - only 1 copy so correct
                      1. flexibility for expanding database in future
                        1. easier to maintain database
                          1. less storage space needed, so smaller hard drive
                          2. DISADVANTAGES
                            1. reduces database performance - more tables=slower processing
                              1. results of historial calculations can't be stored
                                1. may not meet needs of comapny, e.g. store address as 1 field
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