Procedure with “bind varibale” does not return the desired result set

Question

I have a table with below structure:

create table CUST_MODERN_CHANNEL_BRANCH
(
  customer_Num      NUMBER,
  channel_Code  NUMBER(5)
)

Some example data :

   Customer_Num       Channel_Code
  =============     ==============
       1                 5
       1                 4
       1                 6
       2                 3
       3                 5

I wrote a procedure which you can see the code below :

create or replace procedure query_test(res          out sys_refcursor,
                                       order_by     number,
                                       customer_num number) is
  qry varchar2(1000) := ' select * from cust_modern_channel_branch ';
begin

  if customer_num is not null then
    qry := qry || ' where customer_num = :cust ';
  end if;

  if order_by is not null then
    qry := qry || ' order by :ord ';
  end if;
    
        --******* Generate Result 

  if customer_num is not null then
    if order_by is not null then
      open res for qry
        using customer_num, order_by;
    else
      open res for qry
        using order_by;
    end if;
  end if;
end;

I'm using bind variable in my procedure to protect it from injection and make it better in terms of performance. The problem is that when I TEST my procedure with input parameters customer_num=1 / Order_by=2 the final result is not sorted on the second column and it is like this:

  Customer_Num       Channel_Code
  =============     ==============
       1                 5
       1                 4
       1                 6

But when I write a query with order by, it gives me the output below:

select *
from CUST_MODERN_CHANNEL_BRANCH t
where t.customer_num = 1
order by 2

  Customer_Num       Channel_Code
  =============     ==============
       1                 4
       1                 5
       1                 6

Is that something wrong with my procedure? Or the way I used bind variables? Thanks in advance

Answer 1

order by 2 does not equal to order by :ord where :ord = 2.

With order by 2, 2 represents a position, meaning the result must be sorted always by 2nd column in select list.

With order by :ord, :ord is an expression, which will be evaluated to a value, and sorting will be done by that value, not a column.

If you use order by :ord where :ord = 2, that is handled like like order by '2' (logically, ignore the type difference for now).

Do not bind the order by position.