declare @ TestData varchar(12);
set @TestData = '03EA12J77';
select
    (10 - (sum(
            (((N + 1) % 2) + 1) *
            case
                when substring(@ TestData, N, 1) in ('0','A','K','U') then 0
                when substring(@ TestData, N, 1) in ('1','B','L','V') then 1
                when substring(@ TestData, N, 1) in ('2','C','M','W') then 2
                when substring(@ TestData, N, 1) in ('3','D','N','X') then 3
                when substring(@ TestData, N, 1) in ('4','E','O','Y') then 4
                when substring(@ TestData, N, 1) in ('5','F','B','Z') then 5
                when substring(@ TestData, N, 1) in ('6','G','Q')     then 6
                when substring(@ TestData, N, 1) in ('7','H','R')     then 7
                when substring(@ TestData, N, 1) in ('8','I','S')     then 8
                when substring(@ TestData, N, 1) in ('9','J','T')     then 9
                else 0
            end
            ) % 10)) % 10
from
    dbo.Tally
where
    N <= len(@TestData);

DECLARE @TestData      VARCHAR(12),
        @ControlString CHAR(36)
 SELECT @TestData      = '03EA12J78',
        @ControlString = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'

 SELECT SUM(((N+1)%2+1)*(CHARINDEX(SUBSTRING(@TestData, N, 1),@ControlString)-1))%10
   FROM dbo.Tally
  WHERE N <= LEN(@TestData)

DECLARE @TestData      VARCHAR(12),
        @ControlString CHAR(36)
 SELECT @TestData      = '03EA12J78',
        @ControlString = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'

 SELECT 10-(SUM(((N+1)%2+1)*(CHARINDEX(SUBSTRING(@TestData, N, 1),@ControlString)-1))%10)
   FROM dbo.Tally
  WHERE N <= LEN(@TestData)