I wrote:
> Similarly, '\\%' would be the way to match a literal %. You can
> actually backslash-quote any single character this way in LIKE,
> but % and _ are the only ones where it makes a difference.
Er, check that. Backslash itself also needs quoting in LIKE.
Exercise for the student: if you need to match a literal backslash
in a LIKE pattern, how many backslashes do you have to write in your
query?
regards, tom lane