UPDATE ANAMOLIES IN DB

                                                                Tbl_Staff_Branch

I'll refer to the following table when explaining some concepts

What are update Anomalies

The Problems resulting from data redundancy in an un-normalized database table are collectively known as update anomalies. So any database insertion, deletion or modification that leaves the database in an inconsistent state is said to have caused an update anomaly. They are classified as:

Insertion anomalies:  To insert the details of a new member of staff located at branch B1 into the Tbl_Staff_Branch Table shown above, we must enter the correct details of branch numner B1 so that the branch details are consistent with the values for branch B1 in other rows.
To insert the details of a new branch that currently has no members of staff into the Tbl_Staff_Branch table, it is necessory to enter nulls for the staff details which is not allowed as staffID is the primary key.

Deletion anomalies:  If we delete a row from the Tbl_Staff_Branch table that represents the last member of staff located at that branch, (for e.g. row with Branch numbers B",B3 or B4) the details about that branch are also lost from the Database. 

Modification anomalies:   Should we need to change the address of a particular branch in the Tbl_Staff_Branch table, we must update the rows of all staff located at that branch. If this modification is not carried out on all the relevent rows, the database will become inconsistent.