Also, SQL was designed back when most programming was done in assembler or C. Compared to assembler, SQL is easy. Programming itself has gotten a lot easier since.
SQL was designed by IBM in the 1970s, to run on mainframes. The community by whom and for whom it was developed was focused on PL/I and COBOL and largely didn't use C.
The first implementation of SQL in C was probably Oracle V3 (released in 1983). IBM's equivalent SQL offerings around the same time (SQL/DS for VM/CMS and DB2 for MVS) were written in PL/I dialects and assembly, and COBOL, Fortran and PL/I were supported as application languages. I believe IBM's first forays into using C with SQL was the development of OS/2 EE Database Manager in C, somewhat later in the 1980s. (The current DB2 Linux/Unix/Windows code base is originally descended from OS/2 EE Database Manager.)
I was going by Oracle's "first commercial implementation," as a starting point. I found it it was originally written in Fortran, but later ported to C. I wouldn't have guessed fortran.
Oracle was originally written in fortran and then redone in C, which it has been written in ever since. In fact, when we ported Oracle to the mainframe for the first time we were faced with an issue -- do we rewrite Oracle in assembler (there was no c compiler on the mainframe back then) or do we write a C compiler? We wrote a C compiler.
On a side note, I remember watching an interview or reading an article (probably from Larry Ellison) who said IBM gave 1/3 of it's business to Intel, another 1/3 to Microsoft and the final 1/3 to Oracle. Pretty crazy.
By most accounts Oracle V2 was primarily written in PDP-11 assembler. Tom Kyte's suggestion it was written in Fortran contradicts most other sources.
IBM's problem was that they were slow to commercialise the technology despite having a significant head start. IBM built multiple prototype RDBMS systems but they weren't willing to ship the result as a commercial product, and Oracle beat them to it. And even then when they did finally ship, their initial offerings were restricted to their mainframe systems (first VM/CMS and then MVS), while Oracle back then was open to porting their database to just about anything. IBM didn't really come to the cross-platform party until the 1990s, by which time Oracle was well established in that market.
(Disclaimer: Former Oracle employee, although I never worked on the database side of the business, and I'm talking about stuff that happened when I was a kid, or even before I was born.)
