Conditional Entry When Creating Table - sql

Question

I have done this and it works.
CREATE TABLE Employee (
Employee_ID varchar2(10) PRIMARY KEY NOT NULL,
Office_ID varchar2(7) NOT NULL,
Emp_FirstName varchar2(20) NOT NULL,
Emp_LastName varchar2(20) NOT NULL,
Emp_Gender varchar2(1) NOT NULL,
Emp_DateOfBirth Date NOT NULL,
Hire_Date date NOT NULL,
Emp_CurrentDate date default sysdate,
Emp_Telephone varchar2(11) NOT NULL,
Emp_Email varchar2(30) NOT NULL,
Emp_AddressLine varchar2(50) NOT NULL,
Emp_PostCode varchar2(8) NOT NULL,
Emp_Speciality varchar2(20) NOT NULL,
Emp_Qualification varchar2(20) NOT NULL,
Emp_AwardingBody varchar2(30) NOT NULL,
Emp_Salary number(6) NOT NULL,
Emp_Supervised_By varchar2(10) NOT NULL,
Employment_History1 varchar2(50),
Employment_History2 varchar2(50),
Employment_History3 varchar2(50) ,
CONSTRAINT fk_staff_office FOREIGN KEY (Office_ID) REFERENCES office (Office_ID),
CONSTRAINT Hire_Date_CK check (Hire_Date < Emp_CurrentDate AND (Hire_Date - Emp_DateOfBirth)/365 > 18),
CONSTRAINT Emp_DateOfBirth_CK check (Emp_DateOfBirth > TO_DATE('1900-01-01', 'YYYY-MM-DD')),
CONSTRAINT Emp_Salary_CK check (Emp_Salary > 0 AND Emp_Salary < 150000),
CONSTRAINT Emp_Gender_CK CHECK (Emp_Gender in ('M','F')),
CONSTRAINT Emp_Email_CK CHECK ( Emp_Email like '%_#__%._%'),
CONSTRAINT Emp_Telephone_CK CHECK (regexp_like(Emp_Telephone, '^[0123456789]{11}$') AND Emp_Telephone like '0%'),
CONSTRAINT Emp_FirstName_CK CHECK (regexp_like(Emp_FirstName, '^[ABCDEFGHIJKLMNOPQRSTUVWXYZ]{1,20}$')),
CONSTRAINT Emp_LastName_CK CHECK (regexp_like(Emp_LastName, '^[ABCDEFGHIJKLMNOPQRSTUVWXYZ]{1,20}$')),
CONSTRAINT Emp_PostCode_CK CHECK (regexp_like ( Emp_PostCode , '([Gg][Ii][Rr] 0[Aa]{2})|((([A-Za-z][0-9]{1,2})|(([A-Za-z][A-Ha-hJ-Yj-y][0-9]{1,2})|(([A-Za-z][0-9][A-Za-z])|([A-Za-z][A-Ha-hJ-Yj-y][0-9]?[A-Za-z]))))\s?[0-9][A-Za-z]{2})')),
CONSTRAINT Emp_Speciality_CK CHECK (regexp_like(Emp_Speciality, '^[ABCDEFGHIJKLMNOPQRSTUVWXYZ ]{1,20}$')),
CONSTRAINT Emp_Qualification_CK CHECK (regexp_like(Emp_Qualification, '^[ABCDEFGHIJKLMNOPQRSTUVWXYZ ]{1,20}$')),
CONSTRAINT Emp_AwardingBody_CK CHECK (regexp_like(Emp_AwardingBody, '^[ABCDEFGHIJKLMNOPQRSTUVWXYZ ]{1,30}$'))
);
What I want to do now is to create a constraint that enables me to set the value of the attribute Emp_Supervised_By automatically as the same value of the Employee_ID attribute when the Emp_Speciality is 'Manager'.
I tried to do it like this but it doesn't work:
CONSTRAINT Emp_Supervised_By_CK check (CASE WHEN Emp_Speciality = 'MANAGER' THEN Emp_Supervised_By = Employee_ID)
Is a requirement to use CONSTRAINTS NOT TRIGGERS.

Answer 1

Because you mentioned computed columns, maybe your business requirement can be satisfied with the below instead of a constraint.
CREATE TABLE Employee (
...
Employee_ID varchar2(10) PRIMARY KEY NOT NULL,
Emp_Speciality varchar2(20) NOT NULL,
Emp_Supervised_By AS (CASE WHEN Emp_Speciality = 'Manager' THEN Employee_ID ELSE NULL END)
....
);

Answer 2

I did this and it works:
CREATE TABLE OrderLine (
Invoice_ID varchar2(10) PRIMARY KEY NOT NULL,
Item_ID varchar2(10) NOT NULL,
Unit_Price number(6,2) NOT NULL,
Quantity number(6) NOT NULL,
Total_Price number(38,2) AS (CASE WHEN Quantity >= 50 THEN
((Unit_Price*Quantity)-((Unit_Price*Quantity)*0.80)) ELSE Unit_Price*Quantity END) NOT NULL,
CONSTRAINT fk_item_invoice FOREIGN KEY(Invoice_ID) REFERENCES Invoice (Invoice_ID),
CONSTRAINT fk_item_item FOREIGN KEY(Item_ID) REFERENCES Item (Item_ID),
CONSTRAINT Unit_Price_CK CHECK (Unit_Price > 0),
CONSTRAINT Quantity_CK CHECK (Quantity > 0),
CONSTRAINT Total_Price_CK CHECK (Total_Price > 0)
);
CREATE TABLE Invoice (
Invoice_ID varchar2(10) PRIMARY KEY NOT NULL,
Office_ID varchar2(7) NOT NULL,
Invoice_Date Date NOT NULL,
Total_Cost number (9) NOT NULL,
CONSTRAINT fk_order_Office FOREIGN KEY(Office_ID) REFERENCES Office (Office_ID),
CONSTRAINT Total_Cost_CK CHECK (Total_Cost > 0)
);
I want to calculate The TotalCost like the sum of TotalPrice(s).
Is there a way to use the same approach ass before ?