شرح الكودات - محتاجهم جدا

بسم الله الرحمن الرحيم

اخوني الاحباء هل ممكن ششرح الكودات الاتية بالتفصيل ولكم جزل الشكر والتقدير

declare
 cursor cur3 is select *from emp;
 cursor cur4 is select* from dept;
begin
for m in cur3 loop
 for n in cur4 loop
 if m.deptno=n.deptno and m.job='ANALYST' then
 dbms_output.put_line(m.empno||'    '||m.ename||'    '||n.dname||'    '||n.loc);
 end if;
 end loop;
end loop;
end;
/

declare
 cursor cur1 is select empno,ename,job,sal,comm from emp where job='&job';
 emprec cur1%rowtype;
 cnt number;
begin
 open cur1;
 loop
    fetch cur1 into emprec;
    exit when cur1%notfound;
    insert into emp_dup(eno,ename,design,pay,comm) values(emprec.empno,emprec.ename,emprec.job,emprec.sal,emprec.comm);
 end loop;
 commit;
 cnt:=cur1%rowcount;
 close cur1;
 if cnt=0 then
 raise_application_error(-20010,'SORRY NO JOB WITH THIS NAME');
 else
 dbms_output.put_line(cnt||'  are inserted into the emp_dup table');
 end if;
 exception
 when dup_val_on_index then
 dbms_output.put_line('constraints are imposed on emp_dup table');
 end;
/
    --------------------------------------------------------------------
--cursor to retrieve the records from emp,dept and insert into emp_dept_dup
declare
 cursor cur1 is select empno,ename,job,hiredate,sal,comm,sal+nvl(comm,0),dname,loc from emp,dept where emp.deptno=dept.deptno;
 e_d_r cur1%rowtype;
begin
 open cur1;
   loop
  fetch cur1 into e_d_r;
  exit when cur1%notfound;
  insert into emp_dept_dup values(e_d_r.empno,e_d_r.ename,e_d_r.job,e_d_r.hiredate,e_d_r.sal,e_d_r.comm,e_d_r.sal+nvl(e_d_r.comm,0),e_d_r.dname,e_d_r.loc);
   end loop;
   commit;
   close cur1;
end;
/

 cursor mycur1 is select * from emp where deptno=10 for update of sal nowait;
 myrec emp%rowtype;
begin
 open mycur1;
 loop
   fetch mycur1 into myrec;
   if myrec.job='MANAGER' then
  update emp set sal=sal+100 where job='MANAGER';
  commit;
   end if;
   exit when mycur1%notfound;
 end loop;
 dbms_output.put_line('No of Record updated: '||mycur1%rowcount);
 close mycur1;
end;
/

declare
 cursor mycur1 is select * from emp where deptno=&deptno;
 emprec emp%rowtype;
 s number:=0;
 a number;
 cnt number;
begin
 open mycur1;
 loop
	  fetch mycur1 into emprec;
	  exit when mycur1%notfound;
	  dbms_output.put_line(emprec.empno||'  '||emprec.ename||'  '||emprec.sal);
	  s:=s+emprec.sal;
   end loop;
   cnt:=mycur1%rowcount;
   close mycur1;
   if cnt=0 then
   raise_application_error(-20010,'SORRY NO DEPTNO EXIST');
   else
   dbms_output.put_line('Sum of salary  : '|| s);
  a:=trunc(s/cnt,0);
  dbms_output.put_line('Average of salary : '||a);
   end if;
end;
/

   cursor cur1 is select * from emp;
   cursor cur2 is select * from dept;
   emprec emp%rowtype;
   deptrec dept%rowtype;
begin
   open cur1;
   loop
	  fetch cur1 into emprec;
	  exit when cur1%notfound;
	  dbms_output.put(emprec.empno||'  '||emprec.ename||'  '||emprec.sal);
	  open cur2;
	  loop
		    fetch cur2 into deptrec;
		    exit when cur2%notfound;
				    if emprec.deptno=deptrec.deptno then
				    dbms_output.put_line('  '||deptrec.dname||'    '||deptrec.loc);
				    end if;
	  end loop;
	  close cur2;
   end loop;
   close cur1;
end;
/