A database server is a computer program that provides database services to other computer programs or computers, as defined by the client–server model. The term may also refer to a computer dedicated to running such a program. Database management systems frequently provide database server functionality, and some DBMSs (e.g., MySQL) rely exclusively on the client–server model for database access.
Such a server is accessed either through a "front end" running on the user’s computer which displays requested data or the "back end" which runs on the server and handles tasks such as data analysis and storage.
In a master-slave model, database master servers are central and primary locations of data while database slave servers are synchronized backups of the master acting as proxies.
Some examples of proprietary database servers are Oracle, DB2, Informix, and Microsoft SQL Server. Examples of GNU General Public Licence database servers are Ingres and MySQL. Every server uses its own query logic and structure. The SQL query language is more or less the same in all the database servers.