MySQL is a relational database management system (RDBMS) which has more than 11 million installations. The program runs as a server providing multi-user access to a number of databases.
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Transact-SQL (T-SQL) is Microsoft's and Sybase's proprietary extension to SQL. Microsoft's implementation ships in the Microsoft SQL Server product. Sybase uses the language in its Adaptive Server Enterprise, the successor to Sybase SQL Server.
MySQL vs Firebird, 
