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The worst database as my prespective

by mahmoud helmy mahmoud

I think that the worst database is which that has redundant data
which lead to increase the database size and decrease the performance


what leads to redundant data ?

There are many causes that lead to redundant data such as taking the foreign key as many attributes from another table without needing that
for example

suppose we have the tables

1- Employee(ID,Name,Salary,DeptID) // DeptID attribute is foreign key and it is sufficient to make a relation

2- Department(ID,Name,Position)

some one may do this bad design of entity(table)
1- Employee(ID,Name,Salary,DeptID,DeptName) // the value of DeptID may be existed many time,
and due to this DeptName will be repeated without any need
2- Department(ID,Name,Position)
this bad design leads to increase the size of the database and decrease the quality


Thanks in advance

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