LOAD CSV
    FROM INLINE (f1, f2 null if "", f3)
    INTO postgresql://dim@localhost:54393/dim?nulls (f1, f2, f3)
    WITH truncate,
         fields optionally enclosed by '"',
         fields escaped by double-quote,
         fields terminated by ','

  BEFORE LOAD DO
   $$ drop table if exists nulls; $$,
   $$ create table if not exists nulls (id serial, f1 text, f2 text, f3 text); $$;

"quoted empty string","","should be empty string when the CSV parser is improved"
"empty string",,"should be null"
"quoted blanks","    ","should be blanks"
"blanks",    ,"should be null"
"quoted separator","a,b,c","should be 'a,b,c'"