how to find even position letters and odd position lettes in a record in ORACLE - oracle

Question

Please find below the rule of calculating the check digit. The customer number will be 8 digit number. The first 7 digits will be a series and the 8th digit will be a check digit as demonstrated below:
Add all the odd position digits of the running number
Add all the even position digits of the running number
Multiply the sum of above two
Take the modulo 10 of the sum
So as per the above rule the first account number will be:
First part : 0030001
Sum of odd position digits : 0+3+0+1=4
Sum of even position digits : 0+0+0=0
Product of above two sums : 4x0 = 0
Modulo 10 of above product = 0
The complete account number = 00300010
Second account number:
First part : 0030002
Sum of odd position digits : 0+3+0+2=4
Sum of even position digits : 0+0+0=0
Product of above two sums : 4x0 = 0
Modulo 10 of above product = 0
The complete account number = 00300020
Also the following thing to be maintained in the account number format
Length each account has to be of 8 digits (seven digit running number and one check digit, the last digit)
Leading zeros has to be there
The running number must start from 30001

Answer 1

Taking the oracle tag as a hint (and not yet allowed to comment)…
WITH
Input (str, note) AS (
SELECT '00300010', 'OK' FROM DUAL UNION ALL
SELECT '00300020', 'OK' FROM DUAL UNION ALL
SELECT '00300025', 'check digit wrong' FROM DUAL UNION ALL
SELECT '00200010', '< 30001' FROM DUAL UNION ALL
SELECT '0300010', 'too short' FROM DUAL UNION ALL
SELECT '000200010', 'too long' FROM DUAL UNION ALL
SELECT 'a0300025', 'not a number' FROM DUAL
)
SELECT
str
, note
, CASE
WHEN REGEXP_REPLACE(str, '\d{8}', '', 1, 1, '') IS NULL AND
TO_NUMBER(SUBSTR(str, 1, 7)) > 30000 AND
MOD((TO_NUMBER(SUBSTR(str, 1, 1)) +
TO_NUMBER(SUBSTR(str, 3, 1)) +
TO_NUMBER(SUBSTR(str, 5, 1)) +
TO_NUMBER(SUBSTR(str, 7, 1)))
*
(TO_NUMBER(SUBSTR(str, 2, 1)) +
TO_NUMBER(SUBSTR(str, 4, 1)) +
TO_NUMBER(SUBSTR(str, 6, 1))),
10)
= TO_NUMBER(SUBSTR(str, 8, 1))
THEN 'TRUE'
ELSE 'FALSE'
END valid
FROM Input
;
returns
| STR | NOTE | VALID |
|-----------|-------------------|-------|
| 00300010 | OK | TRUE |
| 00300020 | OK | TRUE |
| 00300025 | check digit wrong | FALSE |
| 00200010 | < 30001 | FALSE |
| 0300010 | too short | FALSE |
| 000200010 | too long | FALSE |
| a0300025 | not a number | FALSE |
SQL Fiddle
Which uses SUBSTR(str, 1, 1) to get the respective figures…