Personally I would be comfortable working in a job as you've described. I did a similar project, actually. I've taken SQL and Database design courses purely for my own interest and have a working knowledge of basic Database theory, normalization, RDBMSes, joins, views, and so forth.
Knowing Perl and SQL, it was a snap to pick up DBI, especially with a little help from our friends at O'Reilly. I hit a few little bumps in the road but all in all the customer was ecstatic with the end product and the Engineer in charge of the larger project offered (unsolicited) to provide a reference.
So in answer to your question, yes there are people who would be comfortable with the position. I did this project as a contract since my day job involves moving equipment around and cleaning hard drives but I think this qualifies as having taken up the dual role.
