88066
Descrição
Mapa Mental por Fiona Faulkner, atualizado more than 1 year ago
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Criado por Fiona Faulkner
mais de 12 anos atrás
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NORMALISATION
- 1NF
- All data is atomic
- Has a PK
- No repeating data/fields
- unique field names
- All data is atomic
- 2NF
- Already in 1NF
- All non-key fields are dependent on the whole PK
- all field data can be found by
looking at entire PK
- all field data can be found by
looking at entire PK
- Already in 1NF
- 3NF
- table is already in 2NF
- No functional dependency between
non-key fields
- table is already in 2NF
- ADVANTAGES
- increased data integrity -
only 1 copy so correct
- flexibility for
expanding
database in future
- easier to
maintain
database
- less storage space needed,
so smaller hard drive
- increased data integrity -
only 1 copy so correct
- DISADVANTAGES
- reduces database
performance - more
tables=slower processing
- results of historial
calculations can't be
stored
- may not meet needs of
comapny, e.g. store
address as 1 field
- reduces database
performance - more
tables=slower processing
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