Inserting into a 1:1 reletationship - oracle

Question

I have two tables. Tables A and B, each has a primary key that is autoincremented and foreign must not be null. Both tables are in a 1:1 relationship.
So, for every record in A there must be a B.
What I can't get working is the inserting into such tables. The error I get is "parent key not found".
I'm new to oracle, so thanks for helping.
Here is a screen of ER:
Here's my insert:
INSERT ALL
INTO NASTAVENI_TARIFU (ZADANI_D, ID_OBJEDNAVKY, ID_DODATKU, ID_TARIF, ID_NABIDKY) VALUES (TO_DATE('2018-01-01', 'yyyy-mm-dd' ), 1, SQ_SMLUVNI_DODATEK.nextval, 2, NULL)
INTO SMLUVNI_DODATKY (PROLONGACE_D,ID_NASTAVENI_TARIFU) VALUES (TO_DATE('2019-12-22', 'yyyy-mm-dd' ), SQ_NASTAVENI_TARIFU.currval)
SELECT * FROM DUAL
Here are the definitions:
CREATE TABLE nastaveni_tarifu (
id_nastaveni_tarifu INTEGER NOT NULL,
zadani_d DATE NOT NULL,
id_objednavky INTEGER NOT NULL,
id_dodatku INTEGER NOT NULL,
id_tarif INTEGER NOT NULL,
id_nabidky INTEGER
);
CREATE TABLE smluvni_dodatky (
id_dodatku INTEGER NOT NULL,
prolongace_d DATE NOT NULL,
id_nastaveni_tarifu INTEGER NOT NULL
);
ALTER TABLE smluvni_dodatky
ADD CONSTRAINT fk_dodatek_nast_tarifu FOREIGN KEY ( id_nastaveni_tarifu )
REFERENCES nastaveni_tarifu ( id_nastaveni_tarifu );
ALTER TABLE nastaveni_tarifu
ADD CONSTRAINT fk_nast_tarifu_dodatek FOREIGN KEY ( id_dodatku )
REFERENCES smluvni_dodatky ( id_dodatku );
CREATE SEQUENCE sq_nastaveni_tarifu START WITH 1 MINVALUE 1 NOCACHE ORDER;
CREATE OR REPLACE TRIGGER tr$ntpreinsert BEFORE
INSERT ON nastaveni_tarifu
FOR EACH ROW
WHEN ( new.id_nastaveni_tarifu IS NULL )
BEGIN
:new.id_nastaveni_tarifu := sq_nastaveni_tarifu.nextval;
END;
CREATE SEQUENCE sq_smluvni_dodatek START WITH 1 MINVALUE 1 NOCACHE ORDER;
CREATE OR REPLACE TRIGGER tr$sdpreinsert BEFORE
INSERT ON smluvni_dodatky
FOR EACH ROW
WHEN ( new.id_dodatku IS NULL )
BEGIN
:new.id_dodatku := sq_smluvni_dodatek.nextval;
END;
... I'm starting to hate Oracle, this shouldn't be that hard :(

Answer 1

As I mentioned, this is a bad design as there's circular reference between two tables.
The problem with your insert all statement is that there's no way the second into clause could see SQ_NASTAVENI_TARIFU.nextval as it can get initialised only when the statement as a whole is completed.
Even if you convert this to 2 insert statements, it wouldn't work because there's no way you could ensure to have a row in one table when the value is dependent on other in each case and also the foreign key columns are declared not null.
Either you define them as NULL and try to first insert nulls and then update it or use a Deferred Constraints as a workaround only.
ALTER TABLE smluvni_dodatky
ADD CONSTRAINT fk_dodatek_nast_tarifu FOREIGN KEY ( id_nastaveni_tarifu )
REFERENCES nastaveni_tarifu ( id_nastaveni_tarifu )
deferrable initially deferred;
ALTER TABLE nastaveni_tarifu
ADD CONSTRAINT fk_nast_tarifu_dodatek FOREIGN KEY ( id_dodatku )
REFERENCES smluvni_dodatky ( id_dodatku ) deferrable initially deferred;
Now, there's another problem with your second Trigger, unless the primary key of the table smluvni_dodatky generated using the sequence sq_smluvni_dodatek can store the same value which was insert into nastaveni_tarifu, the constancy can't be maintained.
Hence in your Trigger tr$sdpreinsert, change the assignment expression to this
:new.id_dodatku := sq_smluvni_dodatek.currval;
Now, running both inserts as separate statements like this would work because the constraint checking is not done until a commit is issued.
INSERT INTO nastaveni_tarifu (
zadani_d,id_objednavky,id_dodatku,id_tarif,id_nabidky
) VALUES (
TO_DATE('2018-01-01','yyyy-mm-dd'), 1,sq_smluvni_dodatek.NEXTVAL, 2,NULL
) ;
INSERT INTO smluvni_dodatky (
prolongace_d,id_nastaveni_tarifu
) VALUES (
TO_DATE('2019-12-22','yyyy-mm-dd'),sq_nastaveni_tarifu.currval);
commit;
DEMO