Problems with redundancy
Apart from unnecessary storage, redundancy leads to some more significant
If one copy of a data item is
— for example, a student changes
his or her name — then the database becomes inconsistent unless
A new data item — for example, a new mark for a student — cannot be
entered without adding some other, potentially unnecessary, information
such as the student’s name.
It may not be possible to delete some data without losing other, unrelated
data, as well (an example is on the next slide).
Jianxin Li (UWA)
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