I would like to add a directory D:\pl-sql to the include path of SQL*Plus so I can then work with files in that directory like, for example, edit them with this command:
EDIT hello.sql
How can I do that?
ORACLE_PATH is the variable you are looking for. (on Unix) and SQLPATH (for windows)
http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b12170/ch3.htm#i1052303
This link explains how you can add to the registry entry for windows..
http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b12170/ch3.htm#i1133354
I'm in the habit of creating shortcuts to sqlplusw.exe in my script folders. Edit the shortcut properties to remove anything from the "Start in" field. I can even add the login info on the command line ("Target") so that I can connect instantly with a double-click.