Nested SQL Server transaction performing cascade delete

Question

Suppose I have a table called Companies that has a DepartmentID column. There's also a Departaments table that has as EmployeeID column. Of course I have an Employee table as well. The problem is that I want to delete a company, so first i have to delete all the employees for every departament and then all the departaments in the company. Cascade Delete is not an option, therefore i wish to use nested transactions. I'm new to SQL so I would appreciate your help.

Answer 1

I'm not sure why you need nested transactions here. You only need one actual transaction:

BEGIN TRAN

DELETE FROM Employee
    FROM Employee
    INNER JOIN Department ON Employee.DepartmentID = Department.DepartmentID
    INNER JOIN Company ON Department.CompanyID = Company.CompanyID
    WHERE Company.CompanyID = @CompanyID

DELETE FROM Department
    FROM Department
    INNER JOIN Company ON Department.CompanyID = Company.CompanyID
    WHERE Company.CompanyID = @CompanyID

DELETE FROM Company
    WHERE Company.CompanyID = @CompanyID

COMMIT TRAN

Note the double FROM, that is not a typo, it's the correct SQL syntax for performing a JOIN in a DELETE.

Each statement is atomic, either the entire DELETE will succeed or fail, which isn't that important in this case because the entire batch will either succeed or fail.

BTW- I think you had your relationships backwards. The Department would not have an EmployeeID, the Employee would have a DepartmentID.

Answer 2

I'm not answering your question, but foreign Keys is the way to go, why is it not an option?

As for nested transactions they are:

BEGIN
  delete from Employee where departmentId = 1;
  BEGIN
     delete from Department where companyId = 2;
     BEGIN
        delete from Company where companyId = 2;
     END
  END
END

Programmatically it looks different of course, but that'd depend on the platform you are using