I read your blog every day, and I have also gone through posts in the archive. Still, I could not find the answer to a question that has been bugging me for a while.
Suppose I have a novel (draft version) and my chapters are stand alone.
Suppose I submit the first chapter, which is polished, to journals accepting unsolicited submissions for fiction. Of course, I would mention it is a novel excerpt.
Suppose it gets published. My question is: in the future, when I will be querying agents, having one chapter out there, published, will be seen as pro or con?
It's seen as a pro. This is called a "publishing credit." It's a Good Thing indeed. And you don't need to mention it's part of a novel in your submission to lit journals.
The reason it's a good thing is that someone else has seen your work, and liked it. That tells me that you can string sentences together nicely, or at least have been able to do so in the past. That's reassuring when you're reading queries.
And for all you crazed rodent-wheel running authors out there: NO you do not NEED publishing credits in a query. It's worse to list idiotic ones (I won honorable mention in the XYZ writing contest!) than to list nothing at all.