Question

SQL allows a foreign-key dependency to refer to the same relation, as in the following example:

create table manager (

employee_ID char(20),

Manager_ID char(20),

primary key employee_ID,

foreign key (manager_ID) references manager(employee_ID) on update cascade )

Here, employee_ID is a key to the table manager, meaning that each employee has at most one manager. The foreign-key clause requires that every manager also be an employee. Explain exactly what happens when a tuple in the relation manager is updated.

Specify all steps that will occur in the above scenario.  

Answer 1