1. Openness
1. SQL Server
can only run on windows, without the slightest openness. The stability of the operating system is very important to the database . Windows9X series products are more focused on desktop applications, and NT server is only suitable for small and medium-sized enterprises. And the reliability, security and scalability of the windows platform are very limited. It's not as tried and tested as unix, especially when dealing with large databases .
2. Oracle
can run on all major platforms (including windows). All industry standards are fully supported. Adopt a completely open policy. Allows customers to choose the most suitable solution. Full support for developers. Oracle database is a large-scale relational database based on structured query language. It uses a language that is convenient for logical management to manipulate a large number of regular data collections. It is one of the most popular client-server architecture databases.
Features of oracle:
1), support multi-user, transaction processing with large transaction volume
2), data security and integrity control
3), provide interface for database operations
4), support distributed transaction processing
5), portability , Compatibility and Connectivity
3. Sybase ASE
can run on all major platforms (including windows). However, due to the low level of integration between Sybase and OS in the early days, more OS and DB-level patches are required for versions below VERSION 11.9.2. In a multi-platform mixed environment, there will be certain problems.
4. DB2
can run on all major platforms (including windows). Best suited for massive data. DB2 is the most widely used at the enterprise level. In the world's 500 largest enterprises, almost 85% use DB2 database servers, and in China, it accounts for about 5% in 1997.
5. MySQL
Mysql can run on all major platforms (including windows).
二、可伸缩性，并行性
1. SQL server
并行实施和共存模型并不成熟，很难处理日益增多的用户数和数据卷，伸缩性有限。
2. Oracle
并行服务器通过使一组结点共享同一簇中的工作来扩展windownt的能力，提供高可用性和高伸缩性的簇的解决方案。如果windowsNT不能满足需要，用户可以把数据库移到UNIX中。Oracle的并行服务器对各种UNIX平台的集群机制都有着相当高的集成度。
3. Sybase ASE
虽然有DB SWITCH来支持其并行服务器，但DB SWITCH在技术层面还未成熟，且只支持版本12.5以上的ASE SERVER。DB SWITCH技术需要一台服务器充当SWITCH，从而在硬件上带来一些麻烦。
4. DB2
具有很好的并行性。DB2把数据库管理扩充到了并行的、多节点的环境。数据库分区是数据库的一部分，包含自己的数据、索引、配置文件、和事务日志。数据库分区有时被称为节点安全性。
5.Mysql 较强的伸缩性
三、安全认证
1. SQL server
没有获得任何安全证书。
2. Oracle Server
获得最高认证级别的ISO标准认证。
3. Sybase ASE
获得最高认证级别的ISO标准认证。
4. DB2
获得最高认证级别的ISO标准认证。
5. Mysql 为自由软件（免费），没有获得任何安全证
四、性能
1. SQL Server
多用户时性能不佳
2. Oracle
性能最高， 保持开放平台下的TPC-D和TPC-C的世界记录。
3. Sybase ASE
性能接近于SQL Server，但在UNIX平台下的并发性要优与 SQL Server。
4. DB2
性能较高适用于数据仓库和在线事物处理。
5. Mysql 支持多用户操作，性能较高
五、客户端支持及应用模式
1. SQL Server
C/S结构，只支持windows客户，可以用ADO、DAO、OLEDB、ODBC连接。
2. Oracle
多层次网络计算，支持多种工业标准，可以用ODBC、JDBC、OCI等网络客户连接。
3. Sybase ASE
C/S结构，可以用ODBC、Jconnect、Ct-library等网络客户连接。
4. DB2
跨平台，多层结构，支持ODBC、JDBC等客户。
5. MySql
支持ODBC for Windows。MySql支持所有的ODBC 2.5函数和其他许多函数，这样就可以用Access连接MySql服务器，从而使得MySql的应用被大大扩展。
MySql可运行在不同的操作系统下。简单地说，MySql可以支持Windows95/98/NT/2000以及UNIX、Linux和SUN OS等多种操作系统平台。这意味着在一个操作系统中实现的应用可以很方便地移植到其他的操作系统下。
Sixth, easy to operate
1. SQL Server
is easy to operate, but only a graphical interface.
2. Oracle
is more complex, and provides GUI and command line at the same time, and the operation is the same under windowsNT and unix.
3. Sybase ASE
is more complex and provides both GUI and command line. However, the GUI is poor, and the status is often not timely. It is recommended to use the command line.
4. DB2
is easy to operate, and provides GUI and command line at the same time, and the operation is the same under windowsNT and unix.
5. mysql has a graphical interface, and provides GUI and command line at the same time.
7. Risk of use
1. The completely rewritten code of SQL server
has undergone long-term testing and continuous delays. Many functions need time to prove. Not very compatible.
2. Oracle
's long-term development experience is fully backward compatible. be widely used. There is absolutely no risk.
3. Sybase ASE
is backward compatible, but the ct-library program is not good for porting.
4. DB2
is widely used in giant enterprises and has good backward compatibility. Low risk
5. There is a certain risk in the backward compatibility of Mysql.