Looping Structures

In PL/SQL, there are several looping structures that you can use to iterate through a set of statements multiple times. Here are the main looping structures in PL/SQL:

1. LOOP :
The 'LOOP' statement creates an unconditional loop.
It continues until an EXIT statement is encountered.
  declare
  a number:= 10;
  begin
  dbms_output.put_line('Normal Loop');
  loop
  dbms_output.put_line(a);
  a:=a+10;
  exit when a>50;
  end loop;
  end;
  /
OUTPUT :
Normal Loop
10
20
30
40
50
PL/SQL procedure successfully completed.

2. WHILE :
The 'WHILE' loop repeats a sequence of statements as long as a certain condition is true.

  declare
  i number(5);
  begin
  i := 1;
  while (i < 6)
  loop
  i := i+1;
  dbms_output.put_line('the seq is '||i);
  end loop;
  end;
  /
OUTPUT :
the seq is 2
the seq is 3
the seq is 4
the seq is 5
the seq is 6
PL/SQL procedure successfully completed.

3. FOR :
  • The 'FOR' loop is used when you know the number of iterations in advance.
  • It is often used with index variables.
    • 
  declare
  i number(10);
  begin
  for i in 1..5 loop
  dbms_output.put_line('the sequence is '||i);
  end loop;
  end;
  /
    OUTPUT :
    the sequence is 1
    the sequence is 2
    the sequence is 3
    the sequence is 4
    the sequence is 5
    PL/SQL procedure successfully completed.

    4. FOR LOOP IN REVERSE: 
    
declare
 i number(3);
 begin
 for i in reverse 5..10 loop
 dbms_output.put_line('the seq is '||i);
 end loop;
 end;
 /
    OUTPUT :
    the seq is 10
    the seq is 9
    the seq is 8
    the seq is 7
    the seq is 6
    the seq is 5
    PL/SQL procedure successfully completed.

    5. Nested loop : 
    
declare
i number(3);
j number(3);
begin
<>
for i in 3..5 loop
<< inner_loop>>
for j in 1100..1101 loop
dbms_output.put_line('outer loop is '||i||' inner loop is '||j);
end loop inner_loop;
end loop outer_loop;
end;
/
    Output :
    outer loop is 3 inner loop is 1100
    outer loop is 3 inner loop is 1101
    outer loop is 4 inner loop is 1100
    outer loop is 4 inner loop is 1101
    outer loop is 5 inner loop is 1100
    outer loop is 5 inner loop is 1101
    PL/SQL procedure successfully completed.


    (PL/SQL - Composite Datatypes)