Useful and in demand database

Their are following DB are available :
Oracle 9i / 10g
DB/2 (IBM Product)
MS-SQL Server 2000/2005/2008
Postgres
MySql
SqlLite(for Light database)

Applying an database is depend on our requirement following application used to
choose Database.
1. Size of data( how much record you handle).
2. Costing (is our capable to apt license version of DB like SQL Server,oracle)
3. Hardware support and Environment (Server configuration and is your system Distributed)
4. Application scope.