Partials will break your heart
Okay, since you're answering, how horrid is it to send a query on a partially written novel? (ducking and running) Honest, I know two authors who landed agents on partials, and it makes it darn hard to think you always have to play by the rules. Truth: if you found a new author with a few chapters of stellar writing and a well-defined synop of the rest, would you really care that it's not finished? Really? Honest?
Short answer: yes I would care
Middle answer: I'd like to have a definition of "landed an agent" and actually see the contract before I totally believe this. Express interest sure. "Send more, we love this" absolutely. But a contract? Braver agents than I!
Longer answer: It's hard to finish a novel well. This is not news to you I bet. It's not news to Miss Snark either. It's heartbreaking to get through 300 pages of a wonderful well written novel and then have it fall apart at then end.
That happens more often than I care to think about.
Just this past week I read a wonderful novel with a great heroine and an interesting setting and a good story. Complex characters. Nice sub plot, good twists. At page 300 it was like the author was abducted by aliens. Splat.
If I'd sold that novel on a partial, the editor would be reading the splat first, not me. And trying to fix it. And not being happy. And remembering this the NEXT time I come to her with a "wonderful novel with a great heroine and an interesting setting and a good story. Complex characters. Nice sub plot, good twists."
In addition-I don't want to clog my roster with partials, half dones and hope to bes. I want to sell work. This is cause I like to buy gin rather than wait for it to be donated to the local Food Pantry. There are many many fewer editors who will buy on partials and an outline than will buy a completed draft. Miss Snark likes to have the best odds possible when taking a manuscript out for a stroll.
So, no. Send your partials to your DDS. Send your completed works to the SSD (Snarkily Selective Diva).