Normalisation upto 3nf

[joybanerjee]

What is Normalisation? normalise upto 3nf with a table.If the concept of nested table is used then will the concept of normalisation be violated?

[susarlasireesha]

The process of normalizing data breaks the data down into smaller and smaller tables to reduce redundancy and make retrieving and managing that data more efficient. In general, if you find that you have the same data going into multiple rows, you probably need to break that data out into a separate table. Some of the benefits of normalizing your data are:

Reducing Disk Storage – Since the smaller tables reduce repeating data, the overall database size is smaller.

Ease of Maintenance – If an item changes, then I can update it in only one place. If my data in not normalized, then I must update every occurrence of that item.

Reduce I/O – To retrieve the data I need, I will be reading smaller amounts of data from the disk. If my data is not normalized, I must pull all the data from the disk to find the piece that I want.

Easier Querying – If I store names as “John Garmany” and I want to know how many friends I have with the first name of “John”, I have to read the all the names and extract the first name from each name. If I store the first name and last name as separate items, I can search through only the first names.

Better Security – In a modern relational database, I can allow a user access to only part of the data. I could restrict access to sensitive data such as social security numbers while still allowing access to data regular users need such as names and addresses.

There is a drawback to normalizing a database. Tables must be joined to recreate the whole date set, when needed. As mentioned before, normalization is a process broken up into steps. At the end of each step, you have a normal form. After the first step, you have First Normal Form. The second step produces Second Normal Form. There are six common steps in the normalization process; however, most systems do not go past Third Normal Form.