88189
Descripción
Fichas por Fiona Faulkner, actualizado hace más de 1 año
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Creado por Fiona Faulkner
hace más de 11 años
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| Pregunta | Respuesta |
| Give 2 characteristics of a table in 1NF (1st normal form) | 1)all data is atomic - cannot besplit up further, e.g. forename/surname 2)there is a primary key in the table 3)there is no repeating data, e.g. fields with the same data in 1 record |
| Give 2 characteristics of a table in 2NF (2nd normal form) | 1)must be in 1NF 2)all non-key fields are dependent on the whole PK field(s) |
| Give 3 charactersitics of a table in 3NF (3rd normal form) | 1)must be in 2NF 2)there is no functional dependency between non-key fields |
| Give 3 advantages of normalisation | 1)removes redundant (repeated) data (data is only stored once) 2)less storage space needed to store database due to no repeated data 3)easier to add tables or fields to database in future |
| Give 2 disadvantages of normalisation | 1)reduces database performance as more tables=longer to process queries 2)results of historical (old) calculations can't be stored |
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