SQL Server
Appearance
Microsoft's entry to the enterprise-level database market, competing against Oracle, IBM, and Sybase. Originally developed in conjunction with Sybase, Microsoft split their development early (year?) and pursued their own design and marketting scheme.
SQL Server uses a variety of SQL called T-SQL, a superset of SQL-92 (ISO standard for SQL, certified in 1992). T-SQL mainly adds support for transactions.
As of this writing (September 2001), SQL Server has ~14% of the commercial database market, according to Gartner Group.