Reverse Of any number,Fibonacci sequence

Question

hi all,
Can i find the reverse of any number and Fibonacci sequence in a SELECT query
without using pl/sql and reverse function.
please reply...

Answer 1

Hi,
extreme wrote:
... can you give me example for both 10g and 11gR2 recursive sub-queriesRecursive sub-queries were introduced in Oaracle 11.2; there are no recursive sub-queries in earlier versions.
Here's one way of getting the reverse of a NUMBER in Oracle 10 (and up):
WITH     got_txt     AS
     SELECT     TO_CHAR (12345, 'TM')     AS txt
     FROM     dual
,     exploded_txt     AS
     SELECT     LEVEL               AS pos
     ,     SUBSTR (txt, LEVEL, 1)     AS a_char
     FROM     got_txt
     CONNECT BY     LEVEL <= LENGTH (txt)
SELECT  TO_NUMBER ( REPLACE ( XMLAGG ( XMLELEMENT ( e
                                          , a_char
                                      ).EXTRACT ('//text()')
                             ORDER BY  pos     DESC
            )     AS reverse_num
FROM    exploded_txt
;As written, this only does one number per query. It can be adapted to do several numbers at the same time, but it's somewhat messier.
Starting in 11.2, you cn also use a recursive sub-query, as show below.
This method can easily handle multiple numebrs in the same query. You'll probably get them from one of your existing tables, not hard-coded in a sub-query, like sample_data, below:
WITH     sample_data AS
     SELECT  12345     AS n     FROM dual     UNION ALL
     SELECT     30.2             FROM dual     UNION ALL
     SELECT     0          FROM dual
,     got_txt (n, step, txt, reverse_txt)     AS
     SELECT     n
     ,     1                    AS step
     ,     TO_CHAR (n, 'TM')          AS txt
     ,     SUBSTR ( TO_CHAR (n, 'TM')
                 , 1
                 , 1
                 )               AS reverse_txt
     FROM    sample_data
    UNION ALL
     SELECT     n
     ,     step + 1          AS step
     ,     txt
     ,     SUBSTR ( txt
                 , step + 1
                 , 1
                 ) || reverse_txt     AS reverse_txt
     FROM    got_txt
     WHERE     step     < LENGTH (txt)
SELECT     n
,     TO_NUMBER (reverse_txt)     AS reverse_n
FROM     got_txt
WHERE     step     = LENGTH (txt)
;A somewhat simpler problem is how to reverse a given string.
As you can see, boith of the approaches above start by converting the given number to a string, and end by converting it back to a NUMBER, to meet your requirements.
Neither version (as posted) handles negative numbers properly. Both can be adapted to do so.