Using differing numbers of inputs for a similar query using DBMS_SQL

Question

Hi,
I'm trying to use DBMS_SQL for a query that's either going to include the following WHERE statement:
"AND sched_requirement_id = pin_sr_id"
or not base upon conditions passed to the procedure calling it
v_sql_stmt :=
'SELECT COUNT(1)
INTO v_exists
FROM SCHED_PSA_REQS
WHERE sched_week_id = pin_sched_week_id
AND sequence_number = pin_seq_no
AND sched_original_req_id = pin_sor_id
----> AND sched_requirement_id = pin_sr_id<---------
AND ROWNUM = 1';
The only reason I can't use NDS for this is because of the pin_sr_id input doesn't exist inside the universe of the v_sql_stmt. If it was an inner join or something I could get away with it.
I read that DBMS_SQL doesn't care how many input values it gets until the dbms_sql.EXECUTE statement, but in all the documentation I've read through I have yet to come across an example that deals with a varying number of input values. Does anyone out there have an example of DBMS_SQL that deals with a varying number of bind input values based upon a conditional statement or input values?
Thanks!

Answer 1

Mike,
Thanks for your input but the EXECUTE IMMEDIATE I would be using contains the following input values:
EXECUTE IMMEDIATE v_sql_stmt
INTO v_psa_req_id USING pin_sched_week_id, pin_seq_no, pin_sor_id, pin_sr_id;
I experimented with exactly what you suggested with scott/tiger:
set serveroutput on
DECLARE
v_target_val NUMBER;
v_str varchar2(4000);
f_tbl varchar2(200);
f_exp varchar2(200);
dept_var NUMBER:= 20;
BEGIN
f_tbl := ', dept d';
f_exp := 'and e.deptno = dept_var ';
--f_exp := ' and e.deptno = d.deptno ';
v_str := ' Select '
||' sal '
||' from emp e '
||f_tbl
||'
where '
||' e.empno = :b_v_for_where_cond '
||f_exp;
dbms_output.put_line(v_str);
EXECUTE IMMEDIATE v_str
INTO v_target_val USING 7369;
dbms_output.put_line(v_target_val);
EXCEPTION
when no_data_found then
dbms_output.put_line('No data exception raised');
when others then
dbms_output.put_line(SQLCODE||' '||SQLERRM);
END;
The code bombs miserably when I try to introduce a variable that's not fed in from the USING clause. From what I've learned of NDS all values must either be deliberately fed in like from the USING statement or must exist "inside the universe" of that SQL statement. Example if I use the line:
f_exp := ' and e.deptno = d.deptno ';
instead it works because d.deptno can be referenced from within that SQL statement from table dept.
So in my case either pin_sr_id is part of the USING clause or it's not. This is the one thing that DBMS_SQL still has over NDS is the fact "It does not need to know the number and types of arguments it will receive and process." (1) Oracle Database 10g PL/SQL Programming pg. 609.
They say you can use DESCRIBE_COLUMNS and DESCRIBE_COLUMNS2. However, I've yet to find an example of its use. If anybody has any web links to such it would be greatly appreciated.