How to choose Database for your application

We are always wondering why or which database we use to build our application. Or more precise, what is the difference between various databases.
I am here taking example of DB2, Oracle and Microsoft SQL Server to show the difference. Below are few point, based on which we or our DBA or Architects decides which database to be used in project

• Operating System: Not all database supports all operating systems.

Database	Supported Operating System
MSSQL	Windows
DB2	Windows, Linus, Unix
Oracle	Windows, Linus, AIX, Solaris, HP-UX



• API's and other access methods:

Database	API
MSSQL	OLE DB, ADO.NET, Jdbc, Odbc
DB2	Json, Xquery, ADO.Net, Jdbc, Odbc
Oracle	ODP.Net, Jdbc, Odbc



• XML support: Not all Database support XML datastructure or, support of XPATH, XQuery or XSLT is missing

Database	Support
MSSQL	No
DB2	No
Oracle	Yes



• Implementation language: 

Database	Language
MSSQL	C++
DB2	C/C++
Oracle	C/C++



• Supported programming languages:

Database	Support language
MSSQL	Java, Dot Net, PHP, Ruby, VB, Python
DB2	Java, Dot Net, PHP, Ruby, VB, Python, Cobol, Fortan, C, C#, C++
Oracle	Java, Dot Net, PHP, Ruby, VB, Python, Cobol, Fortan, C, C#, C++, Groovy, Scala, Tcl



• Limits:
• No of Columns

Database	Number of columns
MSSQL	1024
DB2	1012
Oracle	1000



• Name length

Database	Length
MSSQL	128
DB2	30
Oracle	30



• Number of columns in Indexing

Database	Number of columns
MSSQL	16
DB2	64
Oracle	32



• Recursive Subquery

Database	Recurresive Subquery
MSSQL	32
DB2	224
Oracle	255




• Security: 
• DB2: DB2 is less secure database, vulnerable to users or hackers subverting the security. It is difficult to add layers of security after the product is designed, coded and shipped. It has higher upfront cost, because of the additional products necessary to secure DB2. Hence it has higher long term cost of ownership.
• Oracle: Oracle integrate security feature into each of its product. Customer are not obliged to purchase add on products for fundamental but essential security feature.


• Microsoft Sql server comes as a bundle with below products(MSBI -- Microsoft Business Intelligence)
• Database Engine --> responsible for database related queries
• Analysis Service --> used in Dataware housing and data hiring
• Reporting Service --> used to create enterprise reports
• Integration Service --> used to integrate the data from one data source to another, such as oracle to sql server.

In case of DB2 and Oracle, you have to purchase them separately.