I'd expect this:
\copy tablename from 'filename.csv' WITH NULL as '' CSV HEADER
whould import "" as NULL.
The input file is UTF-8 (not Unicode/UTF-16).
I checked the hexdump and the "wannabe" NULL are actually
2c 22 22 2c -> ,"",
all fields are varchar that admit NULL
but still I get empty strings ('') in spite of NULL.
Am I missing something or it is a well known "feature"?
thx
--
Ivan Sergio Borgonovo
http://www.webthatworks.it