postgresql COPY and CSV data w/ double quotes

While some database products treat an empty string as a NULL value, the standard says that they are distinct, and PostgreSQL treats them as distinct.

It would be best if you could generate your CSV file with an unambiguous representation. While you could use sed or something to filter the file to good format, the other option would be to COPY the data in to a table where a text column could accept the empty strings, and then populate the target table. The NULLIF function may help with that: http://www.postgresql.org/docs/9.1/interactive/functions-conditional.html#FUNCTIONS-NULLIF -- it will return NULL if both arguments match and the first value if they don't. So, something like NULLIF(txtcol, '')::numeric might work for you.

as an alternative, using

sed 's/""//g' myfile.csv > myfile-formatted.csv
psql 
# copy mytable from 'myfile-formatted.csv' with csv header;

works as well.