Problems with Duplicate data:
Wastage of disk space.
DML(Insert/Update/Delete) queries can become slow.
To solve this, we normalize tables. We have broken the above table into 2 tables, repeating columns we have moved into separate table and we don’t have to repeat DName,DHead,DLocation in the Employees Table all we do here refer Did.And we have given primary key to Did to uniquely identify each department in the Department table.