Recursive Stored Procedures - sql

Question

I found this code snipped (Source):
CREATE PROCEDURE rec_fib(n INT, OUT out_fib INT)
BEGIN
DECLARE n_1 INT;
DECLARE n_2 INT;
IF (n=0) THEN
SET out_fib=0;
ELSEIF (n=1) then
SET out_fib=1;
ELSE
CALL rec_fib(n-1,n_1);
CALL rec_fib(n-2,n_2);
SET out_fib=(n_1 + n_2);
END IF;
END
This code works with MySQL. In how far do I have to modify it to run on DB2? I cannot seem to find a running minimal example of an recursive stored procedure for DB2.

Answer 1

This works for me: (I haven't done more than make it work, so alternative coding could also work.)
First, add these two lines:
DECLARE n_3 INT;
DECLARE n_4 INT;
Then modify this small section:
ELSE
set n_3 = n - 1;
set n_4 = n - 2;
CALL rec_fib(n_3,n_1);
CALL rec_fib(n_4,n_2);
That's all. Runs on IBM i 6.1 DB2 UDB.

Answer 2

The following code is from SQL tips for DB2, written by Serge Rielau
CREATE OR REPLACE FUNCTION Fib(n INTEGER) RETURNS DECIMAL(31, 0)
BEGIN
DECLARE res DECIMAL(31, 0);
CASE WHEN n = 0 THEN
SET res = 0;
WHEN n = 1 THEN
SET res = 1;
WHEN n > 1 THEN
BEGIN
DECLARE stmt STATEMENT;
PREPARE stmt FROM 'SET ? = Fib(? - 1) + Fib(? - 2)';
EXECUTE stmt INTO res USING n, n;
END;
ELSE
SIGNAL SQLSTATE '78000' SET MESSAGE_TEXT = 'Bad input';
END CASE;
RETURN res;
END;
/
For more information, please check the source page of this code: https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/recursive_sql_pl?lang=en