If you have never written a novel before, ever, and are querying, should one say that at all? Although I have never recommended that someone attempt to publish the first novel that they have ever written, if someone wanted to, should they just not say anything about previous experience, since it wouldn't apply?
Most writers mention that this is their first novel when they query me. When I read these queries I wonder, first of all, if these writers have done any edits on their work, bothered to revise their novel or whether this is their very first draft. Consequently, if this is your first novel attempt, ever, mention this but also mention that your writing has been thoroughly revised and edited. If you received help from your critique group or if you had your work professionally edited, I would want to know this, and if your work was professionally edited, sharing your editor’s name is also a plus.
To be very honest, experience has shown me that first attempts are usually not commercially viable. The reason for this is that unless writing comes to you naturally, your first attempt as a novelist, as first attempts with just about anything, is not going to be advanced enough to win you a publishing contract. Consequently, most agents, including myself, very seldom consider representing first attempts.
We all learn to write at a very young age. Normally, children who enter first grade know how to write simple sentences. Writing is, after all, a form of communication, so it is assumed that anyone who is literate can write. However, it is a huge leap to assume that anyone who is literate is also a novelist, and I think assuming this is becoming a major problem.
Somewhere in middle school and maybe even before, we write our first composition. Is it natural to think that we could also, at this point, win a publishing contract for a magazine article? I don’t think so. It takes time to hone those skills and learn about the different types of writing out there. It also takes time to hone the skills needed to write a novel.
For a moment I would like to go beyond the question and connect back to the post about including magazine writing in your query for a novel. Keep in mind that composition writing moves one in the direction of magazine articles and creative writing moves one in the direction of short fiction, which can eventually lead to writing longer fiction. As can be seen here, composition and creative writing move on two different tracks. Consequently, since they are not that closely related—more like distant cousins—why put this information in your query letter unless you are querying us on a non-fiction project?
To reiterate the main point of this post, make sure that if you mention you are querying on a first novel that you communicate effectively the steps you have taken to make it the best it can possibly be. Without this information, your query will probably be dismissed. Most agents have seen too many poorly written first novels to believe that yours might be any better, so make sure you give us the information needed to truly understand your writing ability.