Openness:
SQL Server
can only run on windows, there is not the slightest openness, the stability of the operating system system is very important to the database.Windows9X series products are biased towards desktop applications NT server is only suitable for small and medium-sized enterprises. And windows platform reliability, security and scalability is very limited. It is not as well-tested as unix, especially when dealing with big data.
Oracle
Runs on all major platforms (including windows). Fully supports all industry standards. Uses a completely open strategy. Enables customers to choose the most appropriate solution. Full support for developers.
Sybase ASE
Runs on all major platforms, including windows. However, earlier versions of VERSION 11.9.2 and below required more OS and DB-level patches because of Sybase's poor integration with the OS. This can be problematic in mixed environments with multiple platforms.
DB2
Runs on all major platforms (including windows). The most suitable for massive data. DB2 is most widely used in the enterprise , in the world's 500 largest enterprises , almost 85% of the DB2 database server , while the domestic to 97 years about 5%.
Scalability, Parallelism
SQL Server
Parallel implementations and *** storage models are not mature. Difficult to handle increasing number of users and volumes of data. Limited scalability.
Oracle
Parallel Server extends the capabilities of windowsNT by enabling a group of nodes to **** enjoy work in the same cluster, providing a clustered solution with high availability and high scalability. If windowsNT is not sufficient, users can move the database to UNIX. oracle's parallel server has a fairly high level of integration with the clustering mechanisms of various UNIX platforms.
Sybase ASE
While there is DB SWITCH to support its parallel servers, DB SWITCH is not yet mature at the technical level and only supports ASE SERVER of version 12.5 and above, because DB SWITCH technology requires a server to act as a SWITCH.
DB2
Has great parallelism.DB2 expands database management to a parallel, multi-node environment. A database partition is a part of the database that contains its own data, indexes, configuration files, and transaction logs. Database partitions are sometimes called nodes .
Security
SQL Server
does not receive any security certificates.
Oracle Server
is certified to the ISO standard, the highest level of certification.
Sybase ASE
Has received ISO standards certification at the highest certification level.
DB2
Certified to ISO standards at the highest certification level.
Performance
SQL Server
Performs poorly with multiple users
Oracle
Highest performance, holds the world record for TPC-D and TPC-C on an open platform.
Client support and application mode
SQL Server
C/S structure, only support windows clients, can use ADO, DAO, OLEDB, ODBC connection.
Oracle
Multi-level network computing, support for a variety of industry standards, you can use ODBC, JDBC, OCI and other network clients to connect.
Sybase ASE
C/S structure, can use ODBC, Jconnect, Ct-library and other network clients to connect.
DB2
Cross-platform, multi-tier structure, support for ODBC, JDBC and other clients
Easy to operate
SQL Server
Easy to operate, but only graphical interface.
Oracle
more complex, while providing GUI and command line, in windows NT and unix under the same operation
Sybase ASE
more complex, while providing GUI and command line. However, the GUI is poor, often not in a timely state, it is recommended to use the command line.
DB2
Simple to operate, provides both GUI and command line, operates the same under windows NT and unix
Risks of using
SQL Server
Completely rewritten code, underwent a long period of testing, constant delays, and many features need time to prove. Not quite both
Oracle
Long development experience, fully backward compatible. Widely used. Completely risk free.
Sybase ASE
Backwards compatible, but ct-library programs are not portable.
DB2
Widely used in giant enterprises, good backward compatibility. It's less risky.
After the above comparison, it is easy to realize that DB2 is the best database.