ORA-01008: not all variables bound - "not all variables bound" - oracle

Question

This is my plsql block, dynamic SQL. I can't find a reason why it comes up with an error 'no ORA-01008: not all variables bound ORA-06512: at line 23'.
I can't find the error on my EXECUTE IMMEDIATE statement.
DECLARE
form_name VARCHAR2(225) := 'MUST AS';
ad_no VARCHAR2(225) := :ad_no;
sql_stmt VARCHAR2(4000);
sql_output VARCHAR2(4000);
db_table VARCHAR(225) := inp_reminder_pkg.form_db_table(form_name);
col_id VARCHAR(225) := inp_reminder_pkg.get_col_id(form_name);
BEGIN
sql_stmt := '
SELECT :1
FROM #tableName
WHERE advno = :2
AND created = ( SELECT MAX(CREATED)
FROM #tableName
WHERE advno = :2 )'
;
sql_stmt := replace(sql_stmt, '#tableName', db_table);
EXECUTE IMMEDIATE sql_stmt
INTO sql_output
USING col_id, ad_no;
dbms_output.put_line(sql_output);
EXCEPTION
WHEN no_data_found THEN
dbms_output.put_line('no-data');
END;
Let me know what I am missing. thanks you

Answer 1

There are three bind variables (even though two have the same name), you need to send 3 arguments for them in the execute immediate statement.
Note that you probably didn’t mean for the column name to be input as a bind variable, this is something that has to be dynamically executed if you want to have a variable column being selected.

Answer 2

There are two problems with your code:
The dynamic query has two instances of the placeholder :advno so you need to pass two values in the USING clause. Yes this is a bit rubbish, but I guess Oracle felt parsing dynamic SQL is hard enough without asking the compiler to match placeholder names.
We can't pass column names or other identifiers as parameters. We have to break up the statement to reference the column name variable. For the same reason you have the replace() call to substitute the table name.
So you need to change your procedure so it looks like this:
DECLARE
form_name VARCHAR2(225) := 'MUST AS';
ad_no VARCHAR2(225) := :ad_no;
sql_stmt VARCHAR2(4000);
sql_output VARCHAR2(4000);
db_table VARCHAR(225) := inp_reminder_pkg.form_db_table(form_name);
col_id VARCHAR(225) := inp_reminder_pkg.get_col_id(form_name);
BEGIN
sql_stmt := '
SELECT ' || col_id || '
FROM #tableName
WHERE advno = :2
AND created = ( SELECT MAX(CREATED)
FROM #tableName
WHERE advno = :2 )'
;
sql_stmt := replace(sql_stmt, '#tableName', db_table);
EXECUTE IMMEDIATE sql_stmt
INTO sql_output
USING ad_no, ad_no;
dbms_output.put_line(sql_output);
EXCEPTION
WHEN no_data_found THEN
dbms_output.put_line('no-data');
END;