Getting blank result while trying to execute a simple while loop in PL/SQL

Question

This is my PL/SQL WHILE LOOP code below:

SET SERVEROUTPUT ON;

DECLARE
l_check NUMBER;
BEGIN
WHILE (l_check < 5)
LOOP
l_check := l_check + 1;
DBMS_OUTPUT.PUT_LINE(l_check);
END LOOP;
END;

When I executed this while loop, it is showing in the message that PL/SQL procedure successfully completed. However, I'm getting a blank result despite using SET SERVEROUTPUT ON;

APC · Accepted Answer · 2017-08-12 14:59:38Z

1

You haven't initialised l_check so it is NULL the first time it is tested in the WHILE loop. NULL is not less than 5 so the code never enters the loop.

Try to initialize the variable before loop:

SET SERVEROUTPUT ON;

DECLARE
    l_check NUMBER := 0;
BEGIN
    WHILE (l_check < 5)
    LOOP
        l_check := l_check + 1;
        DBMS_OUTPUT.PUT_LINE(l_check);
    END LOOP;
END;

edited Aug 12, 2017 at 14:59

APC

147k20 gold badges180 silver badges289 bronze badges

answered Aug 12, 2017 at 13:57

I3rutt

6025 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

stranger Over a year ago

DECLARE l_check NUMBER := 1; BEGIN WHILE (l_check < 5) LOOP DBMS_OUTPUT.PUT_LINE(l_check); l_check := l_check + 1; END LOOP; END; It worked when I have put DBMS_OUTPUT statement before l_check := l_check + 1;

APC Over a year ago

@stranger - the important change is ` l_check NUMBER := 1;`. Assigning a value to the variable means it's not null when you test the WHILE condition

user5683823 Over a year ago

The initial value (0 or 1 or anything else), where you do that (in the DECLARE section or in the execution section), and when you print the current value of l_check (before or after incrementing it) will have little effect, other than on exactly which values are printed. They all work the same way. If you want values from 1 to 4, or from 1 to 5, etc., you can adjust the initial value, the placement of the PUT_LINE command, and/or the exit condition (l_check < 5 vs. <= 5 etc.)

Collectives™ on Stack Overflow

Getting blank result while trying to execute a simple while loop in PL/SQL

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related