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well hi,i have a ques regarding to sql,.... sql allows a foriegn key dependency to refer to the same relation,as in the following example: create table manager(employee_name char(20)not null manager_name char(20)null,primary key employee_name,foriegn key (manager_name)references manager on deleted cascade) here employee_name is key to the table manager,meaning that each employee has most one manager.the foriegn key clause requires that every manager also be an employee.explain exactly what happens when a tuple in the relation manager is deleted?