create table survey_block_sections (
	block_section_id        integer primary key,
	section_id              integer
                                constraint survey_b_s_section_id_fk
                                references survey_sections,
	answer_description	varchar(400)
);

insert into survey_block_sections(block_section_id, section_id, answer_description)
	select distinct block_section_id, section_id, ''
	from survey_block_questions bq
	where not exists 
	  (select block_section_id from survey_block_sections bs where
	   bs.block_section_id=bq.block_section_id);

alter table survey_block_questions add constraint survey_block_sec_fk foreign key (block_section_id) references survey_block_sections;

alter table survey_block_questions drop(section_id);