how do i cascade updates and deletions in oracle? - sql

Question

I'm trying to follow the examples in my book to cascade updates and deletions but the problem is their syntax doesnt work in oracle DB..
I understand to cascade an update would mean an update to a parent would also update its child and same with deletions.. but i cant figure out the syntax for oracle.. the specific questions from my book are:
7.5 -- Write a CREATE TABLE statement for the EMPLOYEE table. Email is
required and is an alternate key, and the default value of Department is
Human Resources. Cascade updates but not deletions from DEPARTMENT to EMPLOYEE.
7.6 -- Write a CREATE TABLE statement for PROJECT table. The default value for
MaxHours is 100. Cascade updates but not deletions from DEPARTMENT to EMPLOYEE.
7.7 -- Write a CREATE TABLE statement for the ASSIGNMENT table. Cascade only
deletions from PROJECT to ASSIGNMENT; do not cascade either deletions or
updates from EMPLOYEE to ASSIGNMENT.
I finally managed to successfully created these tables in iSQL *Plus with this Query:
CREATE TABLE DEPARTMENT (
DepartmentName char(35) NOT NULL,
BudgetCode char(30) NOT NULL,
OfficeNumber char(15) NOT NULL,
Phone char(12) NOT NULL,
Constraint DepartmentPK PRIMARY KEY(DepartmentName)
);
INSERT INTO DEPARTMENT VALUES (
'Administration', 'BC-100-10', 'BLDG01-300', '360-285-8100');
CREATE TABLE EMPLOYEE (
EmployeeNumber int NOT NULL,
FirstName char(25) NOT NULL,
LastName char(25) NOT NULL,
Department char(35) DEFAULT 'Human Resources' NOT NULL,
Phone char(12) NULL,
Email char(30) NOT NULL,
DepartmentName_FK char(35) NOT NULL,
Constraint EmployeePK PRIMARY KEY(EmployeeNumber),
Constraint EmployeeAK1 UNIQUE(Email),
Constraint DepartmentFK FOREIGN KEY (DepartmentName_FK)
references DEPARTMENT(DepartmentName)
--ON UPDATE CASCADE
--ON DELETE no ACTION
);
CREATE TABLE PROJECT (
ProjectID int NOT NULL,
Name char(30) NOT NULL,
Department1 char(15) NOT NULL,
MaxHours int DEFAULT 100 NOT NULL,
StartDate DATE NULL,
EndDate DATE NULL,
DepartmentName_FK1 char(30) NULL,
Constraint datecheck check (StartDate < EndDate),
Constraint ProjectIDPK PRIMARY KEY(ProjectID),
Constraint DepartmentFK1 FOREIGN KEY (DepartmentName_FK1)
references DEPARTMENT(DepartmentName)
-- ON UPDATE CASCADE
-- ON DELETE no ACTION
);
CREATE TABLE Assignment(
ProjectID Number NOT NULL,
EmployeeNumber Number NOT NULL,
HoursWorked Number NULL,
Constraint ProjectIDEmpNumPK PRIMARY KEY(ProjectID, EmployeeNumber),
constraint ProjectIDFK FOREIGN KEY(ProjectID)
references Project(ProjectID),
constraint EmpNumFK FOREIGN KEY(EmployeeNumber)
references Employee(EmployeeNumber)
--CONSTRAINT UniqueEmployee UNIQUE (EmployeNumber)
--ON DELETE CASCADE
);
but how do I specify cascading delete and update and specify not to?

Answer 1

Did you try this?
CREATE TABLE Assignment(
ProjectID Number NOT NULL,
EmployeeNumber Number NOT NULL,
HoursWorked Number NULL,
Constraint ProjectIDEmpNumPK PRIMARY KEY(ProjectID, EmployeeNumber),
constraint ProjectIDFK FOREIGN KEY(ProjectID)
references Project(ProjectID)
ON DELETE CASCADE
ON UPDATE no ACTION ,
constraint EmpNumFK FOREIGN KEY(EmployeeNumber)
references Employee(EmployeeNumber)
ON DELETE no ACTION
ON UPDATE no ACTION
);