Since COPY uses \N I figured it was a decent choice. <null> or <NULL> came to mind too, but there were long compared to 1, 2, and 4 that appear along side it.
Well, I would use <null>, it doesn't need any explanation and we could use it everywhere else.
I understand that this page we have more NULL values than everywhere else combined, but it's a good opportunity to set a standard for all documentation
If someone writes a patch to make everywhere <null> and changes this page in the process I wouldn't complain. For now there is no such standard, we use empty string everywhere else, and that isn't a good choice here IMO. It is probably a good choice for elsewhere since the empty string is our default. While specific to this page \N reads the best for these examples IMO. But I'll concede to whatever if others think this choice is a review/commit blocker.
