An earlier relational DBMS from Sybase and from Microsoft. Sybase introduced SQL Server in 1988 for various Unix versions. In that same year, with help from IBM, Sybase created an OS/2 version that Microsoft licensed and branded as Microsoft SQL Server. Sybase later ported the product to NT and NetWare, and Sybase and Microsoft sold the same version for NT under their own brand names for several years.

The partnership ended in 1994 with Version 4, and each company continued developing its version of the product separately. Microsoft SQL Server became Microsoft's flagship database software for Windows. In 1997, Sybase turned its version into Sybase Adaptive Server Enterprise, which uses different data stores optimized for specific applications. See ASE.