Sort your nested table data.

Question: How do I sort data which is in a nested table.?

Answer: You might've enjoyed the power of set operations(MINUS,INTERSECT,UNION) in SQL many times.
For example - To combine to sets of data, to eliminate duplicated data among two sets etc.

How about using similar set operations in PL/SQL or Nested tables. ?
With Oracle 10g we can have Multiset operations on Nested tables.

Have you ever come accross a situation, where you need to sort data which is in a nested table.
Below is the sample code to sort nested table and then display it.
---

declare
-- I used one nested table type, which is already available(seeded) in APPS schema.
-- If required, create one table type as you reuired.

v_arr VARCHAR2_TABLE_200 := VARCHAR2_TABLE_200();

begin

v_arr:= VARCHAR2_TABLE_200 ('NEW YORK','SYDNEY', 'SINGAPORE','PERTH', 'NEW DELHI','',NULL,'LONDON');

            -- just print and see, how data is stored in nested table.
                dbms_output.put_line(chr(10)'Cities before sorting..'chr(10)'-----------------------');

for i in v_arr.first..v_arr.last
loop
         dbms_output.put_line(nvl(v_arr(i),'NULL'));

end loop ;

-- watch out NVL function above... wanted to show 'NULL' word, where ever there is NULL.
select cast(multiset(
select * from table(v_arr)
order by 1 asc NULLS FIRST) as VARCHAR2_TABLE_200)
into v_arr from dual;

-- NULLS FIRST in above statement is to display nulls first and then data. Default is nulls displayed last.
-- see if data is sorted or not...

dbms_output.put_line(chr(10)'Cities after sorting..'chr(10)'-----------------------');

for i in v_arr.first..v_arr.last
loop
          dbms_output.put_line(nvl(v_arr(i),'NULL'));
end loop ;
end ;
/

---- here's the output. -------

Cities before sorting..
-----------------------
NEW YORK
SYDNEY
SINGAPORE
PERTH
NEW DELHI
NULL
NULL
LONDON

Cities after sorting..
-----------------------
NULL
NULL
LONDON
NEW DELHI
NEW YORK
PERTH
SINGAPORE
SYDNEY

PL/SQL procedure successfully completed.
..