is it possible to have alphanumeric sequence generator in sql

Question

I need to write a SQL query to print the following aphanumberic sequence in SQL

0001, 0002, ... , 0009, 000A, ... , 000Z, ... , 0010, 0011, ... , 001A, ... and s

Answer 1

-- To get 00000 to ZZZZZ next auto alphanumeric sequence using this function [Please verify before use]
-- This starts from 0-9 then A-Z and then increase next digit from 0-9 then A-Z
-- You need to pass the starting/Last sequence as value to get next sequence  
CREATE OR REPLACE FUNCTION return_next_seq (curr_sequence VARCHAR2)
RETURN VARCHAR2 IS
 retval VARCHAR2(4000) := NULL;
 retMaxval VARCHAR2(4000) := NULL;
 eval_digit CHAR(1) := NULL;
 original_sequence VARCHAR2(4000) := curr_sequence;
 curr1_sequence VARCHAR2(4000) := curr_sequence;
BEGIN
retval := original_sequence;
FOR j IN REVERSE 1..LENGTH(curr1_sequence) LOOP -- Using reverse to know
-- the exact digit position
eval_digit := SUBSTR(curr1_sequence, LENGTH(curr1_sequence));
--IF (ASCII(eval_digit) BETWEEN 49 AND 56) OR
--(ASCII(eval_digit) BETWEEN 97 AND 121) THEN
IF (ASCII(eval_digit) BETWEEN 48 AND 56) OR
(ASCII(eval_digit) BETWEEN 65 AND 89) THEN
eval_digit := CHR(ASCII(eval_digit) +1);
curr1_sequence := SUBSTR(curr1_sequence,1,LENGTH(curr1_sequence)-1);
retval := curr1_sequence || eval_digit || SUBSTR(original_sequence,
LENGTH(curr1_sequence || eval_digit)+1);
EXIT;
ELSE -- move to the next digit leaving the evaluated digit untouched.
    IF (ASCII(eval_digit) = 57) THEN
    eval_digit := CHR(ASCII(eval_digit) +8);
    curr1_sequence := SUBSTR(curr1_sequence,1,LENGTH(curr1_sequence)-1);
    retval := curr1_sequence || eval_digit || SUBSTR(original_sequence,
    LENGTH(curr1_sequence || eval_digit)+1);
    EXIT;
    END IF;
    IF (ASCII(eval_digit) = 90) THEN
        retMaxval :=  eval_digit;
        eval_digit := CHR(ASCII(eval_digit) -42);                                          
        curr1_sequence := SUBSTR(curr1_sequence,1,LENGTH(curr1_sequence)-1);
        FOR k IN REVERSE 1..LENGTH(curr1_sequence) LOOP
            IF (ASCII(SUBSTR(curr1_sequence,LENGTH(curr1_sequence))) BETWEEN 48 AND 56) OR (ASCII(SUBSTR(curr1_sequence,LENGTH(curr1_sequence))) BETWEEN 65 AND 89) THEN
            retval := SUBSTR(curr1_sequence,0,LENGTH(curr1_sequence)-1) || CHR(ASCII(SUBSTR(curr1_sequence,LENGTH(curr1_sequence)))+1) || eval_digit || SUBSTR(retval,
            LENGTH(curr1_sequence || eval_digit)+1);
            ELSE
                IF ASCII(SUBSTR(curr1_sequence,LENGTH(curr1_sequence))) = 57 THEN
                retval := SUBSTR(curr1_sequence,0,LENGTH(curr1_sequence)-1) || CHR(65) || eval_digit || SUBSTR(retval,
                LENGTH(curr1_sequence || eval_digit)+1);
                ELSE
                    IF ASCII(SUBSTR(curr1_sequence,LENGTH(curr1_sequence))) = 90 AND LENGTH(curr1_sequence)>1 THEN
                    retval := SUBSTR(curr1_sequence,0,LENGTH(curr1_sequence)-1) || CHR(48) || eval_digit || SUBSTR(retval,
                    LENGTH(curr1_sequence || eval_digit)+1);
                    curr1_sequence := SUBSTR(curr1_sequence,1,LENGTH(curr1_sequence)-1);
                    retMaxval := retMaxval||'Z';
                    ELSE
                    retMaxval := retMaxval||'Z'; 
                    EXIT;                   
                    END IF;
                END IF;
            END IF;
        END LOOP;
            EXIT;
    ELSE
        curr1_sequence := SUBSTR(curr1_sequence,1,LENGTH(curr1_sequence)-1);
    END IF;
END IF;
END LOOP;
IF retval IS NULL OR (LENGTH(retval) = LENGTH(retMaxval)) THEN
RETURN 'MAX';
END IF;
RETURN retval;
END;

-- To verify, call this function like
SELECT return_next_seq('ZY9Z') FROM dual;
-- Any improvement suggestion is welcome!
--- Thanks!..Sanjiv