Normalization is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anamolies.
Deletion Anamoly : If (S_id) 401 has only one subject and temporarily he drops it, when we delete that row, entire student record will be deleted along with it.
Update Anomaly - Cannot update information without changing information in many places. To update customer information, it must be updated for each sales order the customer has placed.
Read full article from 1NF, 2NF, 3NF and BCNF in Database Normalization
Deletion Anamoly : If (S_id) 401 has only one subject and temporarily he drops it, when we delete that row, entire student record will be deleted along with it.
Update Anomaly - Cannot update information without changing information in many places. To update customer information, it must be updated for each sales order the customer has placed.
Second Normal Form (2NF)
As per the Second Normal Form there must not be any partial dependency of any column on primary key. It means that for a table that has concatenated primary key, each column in the table that is not part of the primary key must depend upon the entire concatenated key for its existence. If any column depends only on one part of the concatenated key, then the table fails Second normal form
{Student, Subject}, Age Third Normal Form (3NF)
Third Normal form applies that every non-prime attribute of table must be dependent on primary key. The transitive functional dependency should be removed from the table.
Boyce and Codd Normal Form is a higher version of the Third Normal form. This form deals with certain type of anamoly that is not handled by 3NF. A 3NF table which does not have multiple overlapping candidate keys is said to be in BCNF.Read full article from 1NF, 2NF, 3NF and BCNF in Database Normalization
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