Suggestion regarding query

Question

Hi,
I have a requirement to select two columns from 6 million rows which is one database, and go through the result set, take the one of the column value as the criteria and select another column from 10000 rows table.
I have used two methods to work. Both are working but they are very slow.
I am using jdbc for this.
First method:
Following is the pseudo code for the same
--Select all rows from the table 1
while (rs.next())
String column1= rs.getString(1);
String Query 2= "Select column2 from table 2 where my_field=column1";
--prepare the statement1 using query2
-- execute the statement1 and copy in to rs1
-- while (rs1.next())
do something
Second method:
In this one instead of querying the database for each row in the first resutl set, used a stored procedure which returns a ref cursor taking the array as the input string.
create or replace type mylist as table of varchar2(20);
create or replace type outlist as table of BLOB;
create or replace package my_pkg
as
type rc is ref cursor;
procedure p(myval_list in mylist, outcur OUT rc);
end;
create or replace package body my_pkg
as
PROCEDURE get_phonetype(myval_list IN imeilist,orefcur OUT rc )
AS
l_data outlist := outlist();
tmp_profile BLOB;
BEGIN
--DBMS_OUTPUT.put_line(myval_list.COUNT);
FOR i IN myval_list.FIRST .. myval_list.LAST
LOOP
BEGIN
SELECT column1 INTO tmp_profile FROM table1 WHERE
column2 IN (SELECT column2
FROM table2
WHERE (column3< myval_list(i) AND column4 > myval_list(i)));
--DBMS_OUTPUT.put_line(tmp_phone);
l_data.extend;
l_data(i) := tmp_profile;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
NULL;
END;
END LOOP;
open outcur for
select * from TABLE( cast (l_data as outlist));
END;
END;
in the java program:
--Select all rows from the table 1
while (rs.next())
--loop few times to populate the column1 string arrays
OracleCallableStatement stmt1=(OracleCallableStatement)conn.prepareCall("{call p(?,?)}");
-- register the out parameter as ORACLETYPES.CURSOR
--prepare the array descriptor for the array, set the array using column1 values
-- set the first argument as array
-- retrieve the result set
--do something with the result set
} //end of while
I thought using the stored procedure would make my process faster, but the second approach deteriated the execution time.
I could not understand where I did the mistake. FOr the 200000 rows for the first table, first approach executed in 10 minutes and the second was taking more than hours.
Can some one help me in fine tuning the stored procedure or suggest an alternative best method.
Regards,
Syam

Answer 1

Syam,
Not knowing your table data or the whole of the queries you're making, this may not be feasible. But could you write this as either a single (albeit complex) query, or perhaps a PL/SQL block that uses a temp table or two, but still does all of the processing in Oracle as queries, not loops?
From the examples you gave, it looks like putting it into one query would just involve a few table joins. But they look like you abbreviated some more complex processing...