create table jobs(job_id INT primary key,
                 job_name varchar(20) not null unique,
                 min_salary numeric(8,2)not null check(min_salary>1500),
                 max_salary numeric(8,2)not null check(min_salary>1500))


create table employees(emp_id INT primary key,
                 first_name varchar(30) not null ,
                 last_name varchar(30) not null ,
                 salary numeric(8,2)not null check(salary>1500),
                       manager_id int references employees(emp_id),
                 job_id int not null references jobs(job_id) deferrable initially deferred);




begin;
insert into employees values(1,'a','b',2000,null,1);
insert into jobs values (1, 'CEO',10000,15000);
commit;

begin;
delete from employees where job_id=3;
rollback;
commit;


begin;
insert into employees values(4,'g','h',2000,1,3);
insert into jobs values (3, 'HR',2000,5000);
commit;