I know that vendors have their own subset of the Original SQL Language that are written in C (Like for Postgre SQL) or MS-SQL Server (C++) etc....
So, was the original SQL written in C, or was it created itself in Assembly? I couldn't really find a definite answer on what it's original language roots are (besides the history and such)
In the late 70s, around the time Ingres was getting started at UC Berkeley, three guys working on a contract for the CIA got together and started a company called Relational Software, Inc.
Their first product was a relational database called Oracle. The
founders decided to use the C language for development. This would
later become important when they decided to start porting to different
platforms.
They also decided to support SQL as the internal data access language.
This would also become a very important factor to its success. In
1979, Relational Software was the only company making an SQL compliant
database. If anyone ever asks you who wrote the first SQL database,
you now know the answer: Oracle.
So the answer is C - according to Burleson Consulting.
1979 - Version 2.0 of Oracle was released and it became first commercial relational database and first SQL database. The company changed its name to Relational Software Inc. (RSI).
1983 - Oracle released version 3.0, rewritten in C language and ran on multiple platforms.
PL/I.
From A History and Evaluation of System R:
The prototype for System R was developed in 1974-75.
A quick history search on Oracle yielded:
So the answer is C - according to Burleson Consulting.
http://www.tutorialspoint.com/sql/sql-databases.htm