These are the insert statements for each table (SQL):

INSERT INTO Prescription (Pat_ID, Pres_Type, Pres_FillDate, Pres_Quant, Pres_Freq) VALUES (20, 'Vasodilator', '2020-08-01', 30, 'Once a day'); INSERT INTO Physician (Supp_ID, Phys_FName, Phys_LName, Phys_Spec) VALUES (123456, 'John', 'Smith', 'Cardiologist'); INSERT INTO Item (Phys_ID, Item_Dose, Item_Color, Item_Size) VALUES (123456, 250, 'White', 'Small'); INSERT INTO Supplier (Supp_Phone) VALUES (124567, 500, 'Green', 'Medium'); INSERT INTO Supplier (Supp_Phone) VALUES (123567, 750, 'Red', 'Large'); INSERT INTO Employee (Pat_ID, Emp_FName, Emp_LName, Emp_Title, Emp_Address) VALUES (20, 'Tom', 'Jones', 'Pharmacist', '123 Main St.'); INSERT INTO Employee (Pat_ID, Emp_FName, Emp_LName, Emp_Title, Emp_Address) VALUES (21, 'Liz', 'Baker', 'Pharmacy Technician', '456 Main St.'); 

I keep getting the same error message for all:

How do i fix this and make the insertion successful?

Error starting at line : 90 in command - INSERT INTO Employee (Pat_ID, Emp_FName, Emp_LName, Emp_Title, Emp_Address) VALUES (20, 'Tom', 'Jones', 'Pharmacist', ' 123 Main St.') Error report - ORA-01400: cannot insert NULL into ("COMP122_W23_VA_23"."EMPLOYEE"."EMP_ID") Error starting at line : 94 in command - INSERT INTO Patient (Pat_FName, Pat_LName, Pat_Allergies, Pat_Gender, Pat_Heigh VALUES ('Gloria', 'Hill', 'Insulin', 'Female', 66, 39, 'Aspirin', '1982-11-27') Error report - 0RA-01400: cannot insert NULL into ("COMP122_W23_VA_23"."PATIENT". "PAT_ID")