plsql学习:loop使用

------example 1: loops with IF statement-----------
set serveroutput on
declare 
    v_counter binary_integer := 0;
    begin
      loop
        --increment loop counter by one
        v_counter := v_counter + 1;
        DBMS_OUTPUT.put_line('v_counter = '||v_counter);
        
        --if exit condition yields true exit the loop
        if v_counter  = 5 then  -- the same as : exit when v_counter = 5;
          exit;
        end if;
        
        end loop;
        --control resumes here
        dbms_output.put_line('Done...');
      end;
     
------example 2: loops with EXIT WHEN conditions-----------
set serveroutput on
declare
    v_course           course.courser_no%type :430;
    v_instructor_id    instructor.instructor_id%type :102;
    v_sec_num          section.section_no%type :=0;
begin
    loop
      --increment section number by one
      v_sec_num := v_sec_num + 1;
      insert into section 
             (section_no,course_no,section_no,instructor_id,
             created_date, created_by,modified_date,
             modified_by)
       values
             (section_id_seq.nextval,v_course,v_sec_num,
             v_instructor_id,SYSDATE,USER,sysdate,user);
       --if number of section added is four exit the loop
       exit when v_sec_num = 4;
     end loop;
     
     --control resumes here
     commit;
end;

--------exiample 3: loops with WHILE Loops condition---------
set serveroutput on 
declare
    c_counter binary_integer := 1;
    v_sum     number :=0;
    begin
      while v_counter <= 10 loop
           v_sum := v_sum + v_counter;
           dbms_output.put_line('current sum is: '||v_sum);
           
           -- increment loop counter by one
           v_counter := v_counter + 1;
      end loop;
      
      -- control resumes here
      dbms_output.put_line('the sum of integers between 1 '||
                           'and 10 is: '||v_sum);
end;

---------example 4: loop with For Loops----------
set serveroutput on
declare
    v_factorial number := 1;
begin
    --the loop counter is defined implicitly by the loop
    --Therefore,before the loop ,the loop counter is undefined and has no value;
    for v_counter in 1..10 loop
      v_factorial := v_factorial * v_counter;
      end loop;
      
      --countrol resume here
      dbms_output.put_line('factorial of ten is :'||v_factorial);
end;