In this article, we will discuss in details about normalization. Generally asked questions is - What is normalization? Why we should use normalization? Is our database is normalized?
Basically, Normalization is the process of organizing data into database efficiently. There are two goals of normalization:-
1- Eliminating redundant data
2- Ensuring data dependencies make sense
The database community has developed a series of guidelines for ensuring that data is normalized in database. These series are
referred to as normal forms and are numbered from 1NF to 5NF. In general practice, we used 1NF, 2NF and 3NF. Occasional we use 4NF. 5NF is very rarely seen and is out of scope this article.
First Normal Form (1NF)
First normal form (1NF) sets the very basic rules for an organized database:
* Eliminate duplicate columns from the same table.
* Create separate tables for each group of related data and identify each row with a unique column or set of columns
Second Normal Form (2NF)
Second normal form (2NF) further addresses the concept of removing duplicative data:
* Meet all the requirements of the first normal form.
* Remove subsets of data that apply to multiple rows of a table and place them in separate tables.
* Create relationships between these new tables and their predecessors through the use of foreign keys.
Third Normal Form (3NF)
Third normal form (3NF) goes one large step further:
* Meet all the requirements of the second normal form.
* Remove columns that are not dependent upon the primary key.
Fourth Normal Form (4NF)
Finally, fourth normal form (4NF) has one additional requirement:
* Meet all the requirements of the third normal form.
* A relation is in 4NF if it has no multi-valued dependencies.
Remember, these normalization guidelines are cumulative. For a database to be in 2NF, it must first fulfill all the criteria of a 1NF database.
I think its enough for this article. I will update this article with practical example soon.
Feature of SQL Server 2008
Most popular question asked by database developers is why we migrated to SQL Server 2008? What is the new feature in 2008 which was not in 2005?
Here is brief summary of the differences and I will try to explain why SQL Server 2008 is rocking.
1- Plug is model for SSMS:- SSMS 2005 also had a plug in model but this was not published.
2- Inline variable assignment:-
Instead of:
DECLARE @myVar int
SET @myVar = 5
you can do it in one line:
DECLARE @myVar int = 5
3- Filtered index:- it allows you to create an index while specifying what rows are not to be in the index. For example, index all rows where Status != null.
4- Intellisense:- in the SQL Server Management Studio (SSMS). This has been previously possible in SQL Server 2000 and 2005 with Intellisense use of 3rd party add-ins like SQL Prompt ($195). But these tools are a horrible hack at best.
Here is brief summary of the differences and I will try to explain why SQL Server 2008 is rocking.
1- Plug is model for SSMS:- SSMS 2005 also had a plug in model but this was not published.
2- Inline variable assignment:-
Instead of:
DECLARE @myVar int
SET @myVar = 5
you can do it in one line:
DECLARE @myVar int = 5
3- Filtered index:- it allows you to create an index while specifying what rows are not to be in the index. For example, index all rows where Status != null.
4- Intellisense:- in the SQL Server Management Studio (SSMS). This has been previously possible in SQL Server 2000 and 2005 with Intellisense use of 3rd party add-ins like SQL Prompt ($195). But these tools are a horrible hack at best.
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