Comparing values from different tables using triggers

Question

so the problem is I have two tables and before inserting or updating the values on one table I have to check if the other table does not contain the new value I'm trying to insert/update like so:

CREATE TABLE categoriasimples(
    nome varchar(64) PRIMARY KEY REFERENCES categoria(nome) ON DELETE CASCADE);

CREATE TABLE supercategoria(
    nome varchar(64) PRIMARY KEY REFERENCES categoria(nome) ON DELETE CASCADE);

CREATE FUNCTION check_categoria_type_sup() RETURNS trigger AS $check_categoria_type_sup$
    BEGIN
        IF nome FROM categoriasimples WHERE (NEW.nome = CategoriaSimples.nome) IS NOT NULL THEN
            RAISE EXCEPTION 'Uma categoria nao pode ser super e simples ao mesmo tempo!';
        END IF;

        RETURN NEW;
    END;
$check_categoria_type_sup$ LANGUAGE plpgsql;

CREATE TRIGGER check_categoria_type_sup BEFORE INSERT OR UPDATE ON supercategoria FOR EACH ROW EXECUTE PROCEDURE check_categoria_type_sup();

CREATE FUNCTION check_categoria_type_simp() RETURNS trigger AS $check_categoria_type_simp$
    BEGIN
        IF nome FROM supercategoria WHERE (supercategoria.nome = NEW.nome) IS NOT NULL THEN
            RAISE EXCEPTION 'Uma categoria nao pode ser simples e super ao mesmo tempo!';
        END IF;

        RETURN NEW;
    END;
$check_categoria_type_simp$ LANGUAGE plpgsql;

CREATE TRIGGER check_categoria_type_simp BEFORE INSERT OR UPDATE ON categoriasimples FOR EACH ROW EXECUTE PROCEDURE check_categoria_type_simp();

I can insert values into one table but if I try to insert in the other table it says:

ERROR: invalid input syntax for type boolean: "bife" (Value that was in the other table) CONTEXT: PL/pgSQL function check_categoria_type_sup() line 3 at IF SQL state: 22P02

Answer 1

This is too long for a comment.

I'm pretty sure you can do what you want without using triggers. I would suggest that you investigate inheritance , which Postgres supports for tables.

You can just define a unique constraint on the parent table and not have to worry about trying to get two different tables to be in sync.