UPDATE c11
SET
c11.completed= c6.completed,
c11.complete_date = c6.complete_date,
-- rest of columns to be copied
FROM courses c11 inner join courses c6 on
c11.userID = c6.userID
and c11.courseID = 11 and c6.courseID = 6
-- and any other checks
I have always viewed the From clause of an update, like one of a normal select. Actually if you want to check what will be updated before running the update, you can take replace the update parts with a select c11.*. See my comments on the lame duck's answer.