Database Reference
In-Depth Information
were left in the database( in detail table) without corresponding parent teacher, the detail
table records would become known as orphaned records. If you want to delete a teacher,
Pawan Kumar from master table than you have to delete all the records associated to Pawan
Kumar in detail table before the deletion from master table.
5.3.3 Update anomaly
Some times an update of a single data value requires multiple rows of data to be updated.
This situation is called update anomaly. Let us take an example of invoice, if a user wanted
to change the customer's address, he would have to change it on every single invoice for
the customer. This is because the customer address would be redundantly stored in every
invoice for the customer. Redundant data needs updation of many copies of the data, but
miss a few of them, which results in inconsistent data. So a skilled database designer cap-
ture an attribute at once, store it once, and use that one copy everywhere.
5.4 NORMALIZATION
Normalization is the process of decomposing and arranging the attributes in a schema,
which results in a set of tables with very simple structures. The main task of normalization
is to make tables as simple as possible. Normalization removes duplication of records
and minimizes redundant chunks of data. Database could be made wellorganized. Physical
space of a computer system can be used very effectively. A database that has undergone
in the process of normalization is one that has been divided into smaller tables to reduce
redundancies and aid in the management of the stored data. The definitions of each level of
