SQL Server 2019

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create function dbo.HinkyBase26( @Value as BigInt ) returns VarChar(15) as
  begin
  -- Notes: 'A' = 0.  Negative numbers are not handled.
  declare @Result as VarChar(15) = '';

  if @Value = 0
    select @Result = 'A';
  else
    set @Value += 1;
  while @Value > 0
    select @Value -= 1, @Result = Char( ASCII( 'A' ) + @Value % 26 ) + @Result, @Value /= 26;
  return @Result;
  end;
create function dbo.DehinkyBase26( @Value as VarChar(15) ) returns BigInt as
  begin
  -- Notes: 'A' = 0.  Negative numbers are not handled.
  declare @Result as BigInt = -1;

  while @Value > ''
    select @Result = ASCII( Left( @Value, 1 ) ) - ASCII( 'A' ) + ( @Result + 1 ) * 26,
      @Value = Right( @Value, Len( @Value ) - 1 );
  return @Result;
  end;
select Arabic, dbo.HinkyBase26( Arabic ) as Alpha,
  dbo.DehinkyBase26( dbo.HinkyBase26( Arabic ) ) as RoundTrip
  from ( values ( 0 ), ( 1 ), ( 25 ), ( 26 ), ( 51 ), ( 52 ),
    ( 27 * 26 - 1 ), ( 27 * 26 ),
    ( 33685567531 ) ) as Foo( Arabic );


Arabic
Alpha
RoundTrip


0
A
0

1
B
1

25
Z
25

26
AA
26

51
AZ
51

52
BA
52

701
ZZ
701

702
AAA
702

33685567531
DEADBEEF
33685567531

Arabic	Alpha	RoundTrip
0	A	0
1	B	1
25	Z	25
26	AA	26
51	AZ	51
52	BA	52
701	ZZ	701
702	AAA	702
33685567531	DEADBEEF	33685567531