execute block
returns (
  TABLE_NAME varchar(32),
  DESCR      varchar(15000))
AS
  declare S  varchar(15000);
  declare S2 varchar(15000);
  declare S3 varchar(15000);
begin
  for
    select
        TRIM(RDB$RELATION_NAME),
        LIST(' or ' || TRIM(RDB$FIELD_NAME) || ' is null',''),
        LIST('case when sum(case when ' || TRIM(RDB$FIELD_NAME) || ' is null then 1 end)>0 then '', '||TRIM(RDB$FIELD_NAME) || ':'' || sum(case when ' || TRIM(RDB$FIELD_NAME) || ' is null then 1 end) else '''' end','||')
      from RDB$RELATION_FIELDS
      where coalesce(RDB$SYSTEM_FLAG,0) = 0
      and coalesce(RDB$NULL_FLAG,0) != 0
      group by 1
    into TABLE_NAME, S, S2
  do
    begin
      DESCR = NULL;
      S3='select '||S2||' from '||TABLE_NAME||' where 1=0 '||S;

      execute statement S3 into DESCR;

      if (char_length(DESCR)>0) then suspend;
    end
end