SELECT INTO variable not working in PL\SQL function - oracle

Question

Not sure why this isn't working, when the base query (the commented out line) does return a value when I pass in the same id - when executed as a straight query outside the function.
Maybe I need to use execute immediate, but not sure why this is returning a "no data" error. I got it working with execute immediate, but interested to know what the issue is with the syntax below.
create or replace FUNCTION "FN_GET_CSP_TEMPLATE_DETAILS" (
TEMPLATE_USED_ID IN VARCHAR2 DEFAULT NULL
)
RETURN VARCHAR2 AS
v_out VARCHAR2(100);
BEGIN
dbms_output.put_line(TEMPLATE_USED_ID);
SELECT i_chronicle_id INTO v_out from TABLE_A where R_OBJECT_ID = TEMPLATE_USED_ID;
-- // this works // SELECT i_chronicle_id INTO v_out from TABLE_A where R_OBJECT_ID = 'ID_99';
dbms_output.put_line(v_out);
return v_out;
end;
So this returns a count of 1:
select count(*) from TABLE_A WHERE R_OBJECT_ID = 'ID_99';
But this returns a null value, function defined as above:
select FN_GET_CSP_TEMPLATE_DETAILS('ID_99') from dual;
This works fine:
create or replace FUNCTION "FN_GET_CSP_TEMPLATE_DETAILS" (
TEMPLATE_USED_ID IN VARCHAR2 DEFAULT NULL
)
RETURN VARCHAR2 AS
v_out VARCHAR2(100);
sql_stmt VARCHAR2(1000);
BEGIN
dbms_output.put_line(TEMPLATE_USED_ID);
sql_stmt := 'SELECT i_chronicle_id from TABLE_A where R_OBJECT_ID = :a';
EXECUTE IMMEDIATE sql_stmt into v_out using TEMPLATE_USED_ID;
dbms_output.put_line(v_out);
return v_out;
end;
Seems it only doesnt work against this production table. If I recreate a dummy table and a function against the dummy table it works.
CREATE TABLE "ANALYTICS"."TEST_CSP_FUNCTION"
( "R_OBJECT_ID" VARCHAR2(20 BYTE),
"I_CHRONICLE_ID" VARCHAR2(20 BYTE)
)
INSERT INTO TEST_CSP_FUNCTION
(R_OBJECT_ID, I_CHRONICLE_ID)
VALUES
('ID_100', 'Doc A');
INSERT INTO TEST_CSP_FUNCTION
(R_OBJECT_ID, I_CHRONICLE_ID)
VALUES
('ID_101', 'Doc B');
INSERT INTO TEST_CSP_FUNCTION
(R_OBJECT_ID, I_CHRONICLE_ID)
VALUES
('ID_102', 'Doc C');
INSERT INTO TEST_CSP_FUNCTION
(R_OBJECT_ID, I_CHRONICLE_ID)
VALUES
('ID_103', 'Doc D');
create or replace FUNCTION "FN_GET_TEST_CSP_TEMPLATE_DETAILS" (
TEMPLATE_USED_ID IN NVARCHAR2 DEFAULT NULL
)
RETURN VARCHAR2 AS
v_out VARCHAR2(100);
BEGIN
dbms_output.put_line(TEMPLATE_USED_ID);
SELECT I_CHRONICLE_ID INTO v_out FROM TEST_CSP_FUNCTION WHERE R_OBJECT_ID = TEMPLATE_USED_ID;
dbms_output.put_line(v_out);
return v_out;
end;
select FN_GET_TEST_CSP_TEMPLATE_DETAILS(N'ID_103') from dual;
returns:
Doc D

Answer 1

It works if row with appropriate ID exists in the table.
Demo:
SQL> select * From table_a;
R_OBJ I_CHRONICLE_ID
----- --------------
id_99 100
Function:
SQL> create or replace function fn_get_csp_template_details
2 (template_used_id in varchar2 default null)
3 return varchar2 as
4 v_out varchar2(100);
5 begin
6 dbms_output.put_line(template_used_id);
7 select i_chronicle_id
8 into v_out
9 from table_a
10 where r_object_id = template_used_id;
11 dbms_output.put_line(v_out);
12 return v_out;
13 end;
14 /
Function created.
Testing:
SQL> set serveroutput on
SQL> select fn_get_csp_template_details('id_99') as result from dual;
RESULT
--------------------------------------------------------------------------------
100
id_99
100
SQL>
If ID doesn't exist, it'll return NULL (if called from SELECT statement, as in my example):
SQL> select fn_get_csp_template_details('ABC') as result from dual;
RESULT
--------------------------------------------------------------------------------
SQL>
It'll return an exception if called elsewhere:
SQL> declare
2 l_result varchar2(100);
3 begin
4 l_result := fn_get_csp_template_Details('ABC');
5 end;
6 /
declare
*
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "SCOTT.FN_GET_CSP_TEMPLATE_DETAILS", line 6
ORA-06512: at line 4
SQL>
That's how it goes. So, what did you do to make it NOT work as expected?