While loops with Strings not Integers - oracle

Question

I'm having trouble finding any information on oracle plSQL while loops with strings online. All seem to be integer. When doing my research i feel i understand the integer aspect of while loops in plSQL but no sites that i have visited touched on or had examples of While Loops using strings.
For example: I can use a For loop to print individual letters from the word 'text' but what would stop me from using a While loop to get the same output?
DECLARE
c1 Number:= 1;
c2 Varchar2(4);
BEGIN
FOR c1 in 1..4
LOOP
SELECT substr('text' , c1 , 1 ) into c2 from dual;
dbms_output.put_line(c2);
END LOOP;
END;
If someone could explain how one would print a individual character or even the whole string with a while loop; or possibly point me in the right direction in terms of where to research example while loops with strings online.
Thank you.

Answer 1

You can write a WHILE loop entirely based on characters - no need for a counter of any kind. Something like this:
declare
txt varchar2(100);
begin
txt := 'my text';
while txt is not null loop
dbms_output.put_line(substr(txt, 1, 1)); -- or whatever else you need to do
txt := substr(txt, 2);
end loop;
end;
/
m
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PL/SQL procedure successfully completed.

Answer 2

Yes, it can be written using a WHILE loop. The crucial thing is the length function and the counter. Also, you don't need a select query.
SET SERVEROUTPUT ON
DECLARE
c1 NUMBER := 1;
txt VARCHAR2(20) := 'text';
BEGIN
WHILE c1 <= length(txt) LOOP
dbms_output.put_line(substr(txt,c1,1));
c1 := c1 + 1; --increment the counter
END LOOP;
END;
/
Result
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PL/SQL procedure successfully completed.

Answer 3

You can use SUBSTR in WHILE loop directly as follows:
SQL>
SQL> set serverout on
SQL> DECLARE
2 C1 NUMBER := 1;
3 C2 VARCHAR2(10) := 'TEXT';
4 BEGIN
5 WHILE SUBSTR(C2, C1, 1) IS NOT NULL LOOP
6 DBMS_OUTPUT.PUT_LINE(SUBSTR(C2, C1, 1));
7 C1 := C1 + 1;
8 END LOOP;
9 END;
10 /
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PL/SQL procedure successfully completed.
SQL>
Cheers!!