Sort Nested table based on dynamic information - oracle

Question

I am having trouble sorted a nested table based on some dynamic information that would be in the order by clause.
Here is a sample of what I have found (https://technology.amis.nl/2006/05/31/sorting-plsql-collections-the-quite-simple-way-part-two-have-the-sql-engine-do-the-heavy-lifting/)
The only difference here is I need to dynamically define the column and direction in the order by clause
SELECT CAST(MULTISET(SELECT *
FROM TABLE(table_a)
ORDER BY P_SORT_COLUMN P_DIRECTION
) as table_typ)
INTO table_b
FROM dual;
So to get around think I thought of using dynamic SQL and put it in a proc as forms cannot do this dynamically
loc_sql_stmt VARCHAR2(500);
BEGIN
loc_sql_stmt := 'SELECT CAST(MULTISET(SELECT * ' ||
'FROM TABLE(P_TABLE_A) ' ||
'ORDER BY P_COLUMN P_DIRECTION || ) as table_typ) ' ||
'INTO P_TABLE_B' ||
'FROM dual;';
EXECUTE IMMEDIATE loc_sql_stmt
USING IN P_TABLE_A, P_COLUMN, P_DIRECTION, P_TABLE_B;
END;
There error I get from the EXECUTE IMMEDIATE line is "ORA-00936 missing expression
So is there a better way to sort a nest table by any given column and the direction or how do I get this dynamic SQL to work?
Here is a sample:
create this in DB:
CREATE OR REPLACE TYPE table_obj AS OBJECT(
column1 VARCHAR2(20),
column2 VARCHAR2(20));
CREATE OR REPLACE TYPE table_typ AS TABLE OF table_obj;
and then a sample run:
DECLARE
table_a table_typ := table_typ ();
table_b table_typ := table_typ ();
loc_idx NUMBER;
loc_sort_column INTEGER := 1;
loc_desc VARCHAR2 (4);
P_SORT_COLUMN VARCHAR2 (100) := 'column1';
P_DIRECTION VARCHAR2 (4) := 'DESC';
loc_sql_stmt VARCHAR2 (500);
BEGIN
FOR i IN 1 .. 5
LOOP
loc_idx := table_a.COUNT + 1;
table_a.EXTEND;
table_a (loc_idx) := table_obj (NULL, NULL);
table_a (loc_idx).column1 := TO_CHAR (loc_idx);
table_a (loc_idx).column2 := TO_CHAR (loc_idx);
END LOOP;
--
loc_sql_stmt :=
'SELECT CAST(MULTISET(SELECT * ' ||
'FROM TABLE(' || table_a || ') ' ||
'ORDER BY ' || P_SORT_COLUMN || ' '|| P_DIRECTION ||
' ) as table_typ) ' ||
'INTO :table_b' ||
'FROM dual';
EXECUTE IMMEDIATE loc_sql_stmt USING IN OUT table_a, table_b;
FOR i IN 1 .. table_b.COUNT
LOOP
DBMS_OUTPUT.PUT_LINE (table_b (i).rx_number);
END LOOP;
END;

Answer 1

To pass variable to native dynamic SQL use : before parameter name, to build dynamic statement use concatenation, like this
loc_sql_stmt VARCHAR2(500);
BEGIN
loc_sql_stmt := 'SELECT CAST(MULTISET(SELECT * ' ||
'FROM TABLE('|| P_TABLE_A || ') ' ||
'ORDER BY ' || P_COLUMN || ', ' || P_DIRECTION || ' ) as table_typ) ' ||
'INTO :P_TABLE_B' ||
'FROM dual;';
EXECUTE IMMEDIATE loc_sql_stmt
USING OUT P_TABLE_B;
END;
EDITED version:
Now seeing your code I understand what you need. To make it work we need to use dynamic PL/SQL block, not Native SQL here is working code of your sample, and pay attention to what is variable and what is concatenated literal
DECLARE
table_a table_typ := table_typ();
table_b table_typ := table_typ();
loc_idx NUMBER;
loc_sort_column INTEGER := 1;
loc_desc VARCHAR2(4);
P_SORT_COLUMN VARCHAR2(100) := 'column1';
P_DIRECTION VARCHAR2(4) := 'desc';
loc_sql_stmt VARCHAR2(500);
BEGIN
FOR i IN 1 .. 5
LOOP
loc_idx := table_a.COUNT + 1;
table_a.EXTEND;
table_a(loc_idx) := table_obj(NULL, NULL);
table_a(loc_idx).column1 := TO_CHAR(loc_idx);
table_a(loc_idx).column2 := TO_CHAR(loc_idx);
END LOOP;
--
loc_sql_stmt := 'begin SELECT CAST(MULTISET(SELECT * ' ||
'FROM TABLE(:table_a ) ORDER BY ' || P_SORT_COLUMN || ' ' ||
P_DIRECTION || ' ) as table_typ ) ' || ' INTO :table_b ' ||
'FROM dual; end;';
EXECUTE IMMEDIATE loc_sql_stmt
USING table_a, IN OUT table_b;
FOR i IN 1 .. table_b.COUNT
LOOP
DBMS_OUTPUT.PUT_LINE(table_b(i).column1);
END LOOP;
END;

Answer 2

If you have limited column/direction choices, try a case statement in your order by, simple example:
select * from tab
order by case when :order = 'c1_asc' then c1 else null end asc
, case when :order = 'c1_desc' then c1 else null end desc
, case when :order = 'c2_asc' then c2 else null end asc
, case when :order = 'c2_desc' then c2 else null end desc
/* ... */
;