Use of FOR Cursor and BULK COLLECT INTO

Question

Dear all,
in which case we prefer to use FOR cursor and cursor with BULK COLLECT INTO? The following contains two block that query identically where one is using FOR cursor, the other is using BULK COLLECT INTO . Which one that performs better given in the existing task? How do we measure performance between these two?
I'm using sample HR schema:
declare
l_start number;
BEGIN
l_start:= DBMS_UTILITY.get_time;
dbms_lock.sleep(1);
FOR employee IN (SELECT e.last_name, j.job_title FROM employees e,jobs j
where e.job_id=j.job_id and  e.job_id LIKE '%CLERK%' AND e.manager_id > 120 ORDER BY e.last_name)
LOOP
  DBMS_OUTPUT.PUT_LINE ('Name = ' || employee.last_name || ', Job = ' || employee.job_title);
END LOOP;
DBMS_OUTPUT.put_line('total time: ' || to_char(DBMS_UTILITY.get_time - l_start) || ' hsecs');
END;
declare
l_start number;
type rec_type is table of varchar2(20);
name_rec rec_type;
job_rec rec_type;
begin
l_start:= DBMS_UTILITY.get_time;
dbms_lock.sleep(1);
SELECT e.last_name, j.job_title bulk collect into name_rec,job_rec FROM employees e,jobs j
where e.job_id=j.job_id and  e.job_id LIKE '%CLERK%' AND e.manager_id > 120 ORDER BY e.last_name;
for j in name_rec.first..name_rec.last loop
  DBMS_OUTPUT.PUT_LINE ('Name = ' || name_rec(j) || ', Job = ' || job_rec(j));
END LOOP;
DBMS_OUTPUT.put_line('total time: ' || to_char(DBMS_UTILITY.get_time - l_start) || ' hsecs');
end;
/In this code, I put timestamp in each block, but they are useless since they both run virtually instantaneous...
Best regards,
Val

Answer 1

If you want to get 100% benifit of bulk collect then it must be implemented as below
declare
     Cursor cur_emp
     is
     SELECT     e.last_name, j.job_title
     FROM     employees e,jobs j
     where     e.job_id=j.job_id
               and  e.job_id LIKE '%CLERK%'
               AND e.manager_id > 120
     ORDER BY e.last_name;
     l_start number;
     type rec_type is table of varchar2(20);
     name_rec rec_type;
     job_rec rec_type;
begin
     l_start:= DBMS_UTILITY.get_time;
     dbms_lock.sleep(1);
     /*SELECT e.last_name, j.job_title bulk collect into name_rec,job_rec FROM employees e,jobs j
     where e.job_id=j.job_id and  e.job_id LIKE '%CLERK%' AND e.manager_id > 120 ORDER BY e.last_name;
     OPEN cur_emp;
     LOOP
          FETCH cur_emp BULK COLLECT INTO name_rec LIMIT 100;
          EXIT WHEN name_rec.COUNT=0;
          FOR j in 1..name_rec.COUNT
          LOOP
               DBMS_OUTPUT.PUT_LINE ('Name = ' || name_rec(j) || ', Job = ' || job_rec(j));          
          END LOOP;
          EXIT WHEN cur_emp%NOTFOUND;
     END LOOP;
        CLOSE cur_emp;
     DBMS_OUTPUT.put_line('total time: ' || to_char(DBMS_UTILITY.get_time - l_start) || ' hsecs');
end;
/