Foreign key keeps saying not enough values - oracle

Question

I have been trying to get this thing working for a few day now (foreign key) and it just don't work, and feel like every solution I used don't work, so i'm asking here to learn what was the problem and how to fix it
Table creation :
CREATE TABLE CUSTOMER
(
Customer_ID varchar(255) NOT NULL,
Customer_Name varchar(50),
Customer_Gender varchar(10),
Customer_DOB varchar(20) ,
CONSTRAINT CUSTOMER_PK PRIMARY KEY(Customer_ID)
) ;
CREATE TABLE PAYMENT
(
Payment_ID varchar(255) NOT NULL,
Cust_ID varchar(255),
Payment_Method varchar(30),
Payment_Date varchar(20),
Payment_Total NUMBER(10,2) ,
CONSTRAINT PAYMENT_PK PRIMARY KEY(Payment_ID),
CONSTRAINT fk_customer FOREIGN KEY(Cust_ID) REFERENCES CUSTOMER(Customer_ID)
) ;
Inserting values :
INSERT INTO CUSTOMER VALUES ('1277','Jenny','Female', ( TO_Date ( '03/04/1988' , 'DD/MM/yyyy')));
INSERT INTO CUSTOMER VALUES ('3423','Bryan','Male', ( TO_Date ( '15/06/1990' , 'DD/MM/YYYY')));
INSERT INTO CUSTOMER VALUES ('4385','Mohd Shafik','Male',( TO_Date ( '20/08/1993' , 'DD/MM/YYYY')));
INSERT INTO PAYMENT VALUES ('24P','Cash', ( TO_Date ( '11/02/2022' , 'DD/MM/YYYY')),24.50);
INSERT INTO PAYMENT VALUES ('09p','Online Transfer', ( TO_Date ( '08/04/2022' , 'DD/MM/YYYY')),25.00);
INSERT INTO PAYMENT VALUES ('10P','Cash', ( TO_Date ( '08/07/2022' , 'DD/MM/YYYY')),22.50);
The foreign keys are now working , but just for life of me can't figure out why the it spits out ORA-00947: not enough values and
ORA-01400: cannot insert NULL into ("SQL_GUUNNGDQAOXJVYPBKNMILVXJR"."PAYMENT"."PAYMENT_ID") ORA-06512: at "SYS.DBMS_SQL", line 1721
Also, Please explain to me how references works, i read a few places but they use words that just confuse me. Please and thank you!

Answer 1

Use DATE data types to store date values (and VARCHAR2 instead of VARCHAR) in your tables:
CREATE TABLE CUSTOMER(
Customer_ID varchar2(255) NOT NULL,
Customer_Name varchar2(50),
Customer_Gender varchar2(10),
Customer_DOB DATE,
CONSTRAINT CUSTOMER_PK PRIMARY KEY(Customer_ID)
);
CREATE TABLE PAYMENT(
Payment_ID varchar2(255) NOT NULL,
Cust_ID varchar2(255),
Payment_Method varchar2(30),
Payment_Date DATE,
Payment_Total NUMBER(10,2) ,
CONSTRAINT PAYMENT_PK PRIMARY KEY(Payment_ID),
CONSTRAINT fk_customer FOREIGN KEY(Cust_ID) REFERENCES CUSTOMER(Customer_ID)
);
Then name the columns in your INSERT statements:
INSERT INTO CUSTOMER (
customer_id, customer_name, customer_gender, customer_dob
) VALUES (
'1277','Jenny','Female', TO_Date('03/04/1988', 'DD/MM/yyyy')
);
INSERT INTO CUSTOMER (
customer_id, customer_name, customer_gender, customer_dob
) VALUES (
'3423','Bryan','Male', TO_Date('15/06/1990', 'DD/MM/YYYY')
);
INSERT INTO CUSTOMER (
customer_id, customer_name, customer_gender, customer_dob
) VALUES (
'4385','Mohd Shafik','Male', TO_Date('20/08/1993' , 'DD/MM/YYYY')
);
Then for the PAYMENT inserts, you have 5 columns in the table but only 4 pieces of data being inserted:
INSERT INTO PAYMENT (
payment_id, payment_method, payment_date, payment_total
) VALUES (
'24P','Cash', TO_Date('11/02/2022', 'DD/MM/YYYY'),24.50
);
INSERT INTO PAYMENT (
payment_id, payment_method, payment_date, payment_total
) VALUES (
'09p','Online Transfer', TO_Date( '08/04/2022' , 'DD/MM/YYYY'),25.00
);
INSERT INTO PAYMENT (
payment_id, payment_method, payment_date, payment_total
) VALUES (
'10P','Cash', TO_Date('08/07/2022', 'DD/MM/YYYY'),22.50
);
You have not provided a Cust_ID value so it will default to NULL in those rows.
If you want to provide a Cust_ID then add it to the statement:
INSERT INTO PAYMENT (
payment_id, cust_id, payment_method, payment_date, payment_total
) VALUES (
'ABC', '1277', 'Cash', TO_Date('08/07/2022', 'DD/MM/YYYY'),22.50
);
db<>fiddle here

Answer 2

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';
CREATE TABLE CUSTOMER
(
Customer_ID varchar(255) NOT NULL,
Customer_Name varchar(50),
Customer_Gender varchar(10),
Customer_DOB DATE ,
CONSTRAINT CUSTOMER_PK PRIMARY KEY(Customer_ID)
) ;
CREATE TABLE PAYMENT
(
Payment_ID varchar(255) NOT NULL,
Customer_ID varchar(255),
Payment_Method varchar(30),
Payment_Date DATE,
Payment_Total NUMBER(10,2) ,
CONSTRAINT PAYMENT_PK PRIMARY KEY(Payment_ID),
CONSTRAINT fk_customer FOREIGN KEY(Customer_ID) REFERENCES CUSTOMER(Customer_ID)
) ;
INSERT INTO CUSTOMER VALUES ('1277','Jenny','Female', ( TO_Date ( '03/04/1988' , 'DD/MM/yyyy')));
INSERT INTO PAYMENT VALUES ('24P','1277','Cash', ( TO_Date ( '11/02/2022' , 'DD/MM/YYYY')),24.50);
SELECT * FROM Customer;
CUSTOMER_ID CUSTOMER_NAME CUSTOMER_GENDER CUSTOMER_DOB
1277 Jenny Female 03-APR-1988
SELECT * FROM payment;
PAYMENT_ID CUSTOMER_ID PAYMENT_METHOD PAYMENT_DATE PAYMENT_TOTAL
24P 1277 Cash 11-FEB-2022 24.5