Basic loop is the simplest form of loop construct in PL/SQL and hence also called as Simple loop. It encloses a sequence of statements between the keywords LOOP and END LOOP. It allows execution of its statements at least once. To keep the loop in finite state the EXIT statement is used.

The EXIT condition can be at the top of the loop or at the end of the loop as per convenience. Depending upon the circumstance we can make use of this loop as Pre-tested or Post-tested loop construct.

SET SERVEROUTPUT ON;

DECLARE
  V_Num NUMBER := 1;
BEGIN
  LOOP
    DBMS_OUTPUT.PUT_LINE('The Line '||V_Num||' Output is '||V_Num);
    V_Num :=V_Num+1;
    IF V_Num > 5 THEN
      EXIT;
    END IF;
  END LOOP;
END;
/

The Line 1 Output is 1
The Line 2 Output is 2
The Line 3 Output is 3
The Line 4 Output is 4
The Line 5 Output is 5
The Total Lines of Output are 5

PL/SQL procedure successfully completed.

DECLARE
  V_Num NUMBER := 1;
BEGIN
  LOOP
  IF V_Num > 5 THEN
    EXIT;
  END IF;
  DBMS_OUTPUT.PUT_LINE('The Line '||V_Num||' Output is '||V_Num);
  V_Num :=V_Num+1;
  END LOOP;
  DBMS_OUTPUT.PUT_LINE('The Total Lines of Output are '||(V_Num-1));
END;
/

The Line 1 Output is 1
The Line 2 Output is 2
The Line 3 Output is 3
The Line 4 Output is 4
The Line 5 Output is 5
The Total Lines of Output are 5

PL/SQL procedure successfully completed.

DECLARE
  V_Number NUMBER := 1;
  V_Output VARCHAR2(100);
BEGIN
  LOOP
    EXIT WHEN V_Number >5;
    V_Output :=V_Output||' '||V_Number;
    V_Number :=V_Number+1;
  END LOOP;
  DBMS_OUTPUT.PUT_LINE('Output Line :'||V_Output);
END;
/

Output Line : 1 2 3 4 5

PL/SQL procedure successfully completed.

DECLARE
  V_Number NUMBER :=1;
  V_Index NUMBER;
  V_Output VARCHAR2(50);
BEGIN
  LOOP
    EXIT WHEN V_Number >5;
    V_Index :=1;
    LOOP
      EXIT WHEN V_Index >V_Number;
      V_Output :=V_Output||'  '||V_Number;
      V_Index :=V_Index+1;
    END LOOP;
    DBMS_OUTPUT.PUT_LINE(V_Output);
    V_Number :=V_Number+1;
  END LOOP;
  DBMS_OUTPUT.PUT_LINE('Output Line :'||V_Output);
END;
/

1                                                                               
1  2  2                                                                         
1  2  2  3  3  3                                                                
1  2  2  3  3  3  4  4  4  4                                                    
1  2  2  3  3  3  4  4  4  4  5  5  5  5  5                                     
Output Line :  1  2  2  3  3  3  4  4  4  4  5  5  5  5  5                      

PL/SQL procedure successfully completed.

DECLARE
  V_Number NUMBER :=1;
  V_Index NUMBER;
  V_Output VARCHAR2(50);
BEGIN
  LOOP
    EXIT WHEN V_Number >5;
    V_Index :=1;
    V_Output :=NULL;
    LOOP
      EXIT WHEN V_Index >V_Number;
      V_Output :=V_Output||'  '||V_Index;
      V_Index :=V_Index+1;
    END LOOP;
    DBMS_OUTPUT.PUT_LINE(V_Output);
    V_Number :=V_Number+1;
  END LOOP;
END;
/
1
1  2
1  2  3
1  2  3  4
1  2  3  4  5

PL/SQL procedure successfully completed.

DECLARE
  V_Number NUMBER :=&GNumber;
  V_Reverse NUMBER :=0;
  V_Temp NUMBER;
  V_Div NUMBER;
BEGIN
  V_Temp :=V_Number;
  LOOP
    EXIT WHEN V_Temp <=0;
    V_Div :=MOD(V_Temp, 10);
    V_Reverse :=V_Reverse*10+V_Div;
    V_Temp :=TRUNC(V_Temp/10);
  END LOOP;
  DBMS_OUTPUT.PUT_LINE('Reverse of '||V_Number||' is : '||V_Reverse);
  IF V_Number =V_Reverse THEN
    DBMS_OUTPUT.PUT_LINE('The number is a Palindrome');
  ELSE
    DBMS_OUTPUT.PUT_LINE('The number isn''t a Palindrome');
  END IF;
END;
/

Enter value for gnumber: 12345
old   2:   V_Number NUMBER :=&GNumber;
new   2:   V_Number NUMBER :=12345;
Reverse of 12345 is : 54321                                                     
The number isn't a Palindrome                                                   

PL/SQL procedure successfully completed.

SQL> /
Enter value for gnumber: 23432
old   2:   V_Number NUMBER :=&GNumber;
new   2:   V_Number NUMBER :=23432;
Reverse of 23432 is : 23432                                                     
The number is a Palindrome                                                      

PL/SQL procedure successfully completed.

SQL> /
Enter value for gnumber: 0
old   2:   V_Number NUMBER :=&GNumber;
new   2:   V_Number NUMBER :=0;
Reverse of 0 is : 0                                                             
The number is a Palindrome                                                      

PL/SQL procedure successfully completed.

SQL> /
Enter value for gnumber: -1221
old   2:   V_Number NUMBER :=&GNumber;
new   2:   V_Number NUMBER :=-1221;
Reverse of -1221 is : 0                                                         
The number isn't a Palindrome                                                   

PL/SQL procedure successfully completed.

--Display all the Months between two given dates using BASIC Loop.

DECLARE
  V_start_date DATE := '01-jan-2010'; --Signifies the Lower date.
  V_end_date   DATE :='31-Aug-2010'; --Signifies the Upper date.
BEGIN
  DBMS_OUTPUT.PUT_LINE('Months between '||V_start_date||' and '||V_end_date||' are :');
  LOOP
    EXIT WHEN V_start_date > V_end_date;
    DBMS_OUTPUT.PUT_LINE(TO_CHAR(V_start_date, 'Month'));
    V_Date1 :=ADD_MONTHS(V_start_date, 1);
  END LOOP;
END;
/

While writing programs using WHILE Loop, you should be very careful about the statement that control the exit from the loop. If the exit from loop condition is never met, the loop becomes infinite and program might go into a deadlock situation.