将 DELETE 级联到另一行 table

Question

CREATE OR REPLACE FUNCTION removerCapitulo()
  RETURNS trigger AS
$BODY$
declare counter int;
BEGIN
select count(*) into counter FROM capitulos where id_capitulo = NEW.id_livro;
if (counter >1)
THEN
DELETE FROM capitulos WHERE id_capitulo = NEW.id_livro;
END IF;
    RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;

CREATE TRIGGER removerCapitulo_trigger
  BEFORE DELETE
  ON livros
  FOR EACH ROW
  EXECUTE PROCEDURE  removerCapitulo();

 DELETE FROM public.livros
    WHERE id_livro = 30

当我尝试删除 ID = id_capitulo 的 "livro" 时，我想删除 "livro" 和 "capitulo"，但是当删除 "livro" 它 returns 成功，但它不会删除 "livro" 或 "capitulo" ...我试着放一个计数器以防 [=] 中有超过 1 个 "capitulo" 23=] 的 id 等于我要求删除它时输入的 id delete

Answer 1

When i try to delete a "livro" with id = id_capitulo i want to delete the "livro" and the "capitulo"

你不需要触发器。相反，您可以使用 on delete cascade 选项的外键：

create table capitulos (
    ...              -- other table columns
    id_capitulo int 
        references livros(id_livro)
        on delete cascade
);

至于你现有的代码：因为你有一个 delete 触发器，你需要使用伪 table old 而不是 new （实际上是空的):

create or replace function remover_capitulo()
returns trigger as
$body$
begin
    delete from capitulos where id_capitulo = old.id_livro;
    return old;
end;
$body$
language plpgsql;

create trigger trg_remover_capitulo
    before delete on livros
    for each row
    execute procedure remover_capitulo();

将 DELETE 级联到另一行 table

Cascade DELETE to row of another table

sql

postgresql

foreign-keys

database-trigger

sql-delete