The data model looks as follows
The SQL Data Definition Statements (DDL) look as follows:
create sequence bo_comment_id_seq; create table bo_comment ( id integer primary Key default nextval('bo_comment_id_seq'::regclass), chapter_id integer not null, comment_id integer, created timestamp with time zone DEFAULT ('now'::text)::timestamp with time zone, email character varying(255) not null, comment_text character varying(2000) not null ) with (oids = false);
Every value of chapter_id must reference to the table bo_chapter. Once a chapter is being deleted on comments are deleted as well. There we define a foreign key with a delete clause.
ALTER TABLE ONLY bo_comment ADD CONSTRAINT comment_chapter_fk FOREIGN KEY (chapter_id) REFERENCES bo_chapter(id) on delete cascade;Next: Building a View Element for the Comments UP: TOC