Database - The Relational Model and Normalization - Discussion
Discussion Forum : The Relational Model and Normalization - General Questions (Q.No. 13)
13.
For some relations, changing the data can have undesirable consequences called:
Discussion:
5 comments Page 1 of 1.
Rajan said:
9 years ago
Why not option 1?
Brijesh singh said:
1 decade ago
Modification anomaly is also called update anomaly which comes when we can modify the attributes a table.
Chandan said:
1 decade ago
Modification anomaly comes when we, say, modify an attribute value and this modification has an undesired effect on the database. Suppose we changed an Attribute Value Dep_name in department table from marketing to research and, in case, this modification leads you to change the attribute value DName to 'Marketing' in Manager table as well (Because Dep_name in Department Table was a PK and DName in Manager table was an FK).
So, as a solution to this problem you need to choose another unique attribute 'Dnum' in both the tables as PK and FK correspondingly such that a change of attribute value similar to above will have no effect in the tables which are referring to the department table on DNum attribute.
So, as a solution to this problem you need to choose another unique attribute 'Dnum' in both the tables as PK and FK correspondingly such that a change of attribute value similar to above will have no effect in the tables which are referring to the department table on DNum attribute.
Amardeep said:
1 decade ago
This is also called update anomalies this problem due to there is no primary key in a relational.
Bharati said:
1 decade ago
What is meant by modification anomalies?
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