It was originally created for UNIX platforms in 1987. In 1988, SQL Server for OS/2 was codeveloped for the PC by Sybase, Microsoft, and Ashton-Tate. Ashton-Tate divested its interest and Microsoft became the lead partner after porting SQL Server to MS Windows NT.
Microsoft and Sybase sold and supported the product through version 4.21. In 1993 the codevelopment licensing agreement between Microsoft and Sybase ended and the companies parted ways.
In 1995, Sybase released SQL Server 11.0. Thereafter, it decided to better differentiate its product from Microsoft SQL Server by renaming it to Adaptive Server Enterprise in versions 11.5 and beyond.
Further History... Sybase was founded by Bob Epstein, the architect of a product called the Intelligent Database Machine (IDM) from Britton-Lee. This was a computer that only did relational database. It used IDL as its native language (similar but not identical to SQL). The architecture of that product was used as the starting point for Sybase, which began development from 1984(?). Beta testing of Sybase's first product started in 1986.