[CaptainZapp]

SQL Server was Sybase until (I think) version 4.9, just rebranded as Microsoft SQL Server.

Then the two versions split and I don't think that any of the Sybase source code remains in what is SQL Server today.

That said, a lot of the concepts (like a significant number of system stored procedures) and also TSQL remain almost the same, with small differences (except for system functions, which SQL Server has a lot more functionality).

When you come from the Sybase world getting a start on SQL Server is quite straight forward when it comes to handling the database.

Internals and other low level nuts and bolts differ nowadays, of course.

[pjmlp]

I wrote a connector for Sybase back in 2000, based on our existing one for MS SQL Server 7, and some things had already changed on the protocol level.

I don't remember exactly what and why, just that for some specific DML commands another kind of connection was required.

[CaptainZapp]

The split must have happened in the mid nineties (I think) with SQL Server 6 and Sybase 10. The next version after 4.9.

It's notable that 10 was the worst Sybase version, ever.

Source: I worked for Sybase Professional Services from 95 - 99.