When using M x sql-postgres to launch the SQL mode window, emacs (as of 25.x) seems to be making smart choices about where the SQL run-time window will show. That is, it splits the viewport and shows the runtime at the bottom by default. But when I resize emacs to full screen (or enough width), SQL runtime shows on the right hand side. My question is:
Can one make the new SQL run time window to always appear at the bottom?
(I observed similar behavior for python and other programming modes when launching the runtime window. Sometimes, I just felt it easier that the runtime always pop up at the same location.)
split-width-threshold. It sounds like you might want to set it higher than the width of a full screen Emacs.