Question

A friend asked how in SQL to convert a varchar which represents an octal value into integer, so I’m placing an answer here and seeing if anyone improves upon it.

I had hoped for a solution that could be run inline as part of query, without having to create any function in the database (e.g if you only have permission to query a database, but not create any new functions or stored procedures in it).

Alternatively, I see that .Net Framework ToInt32 method has easy way of doing this, but seems like jumping through a lot of CLR integration hoops required to get there.

Answer 1

Somewhat convoluted – requiring a 2-level scalar subquery

Setup & Query

declare @t table (oct varchar(10));
insert @t select '7101';
insert @t select '6';
insert @t select '110111';

select *,
       (select sum(val)
        from
           (
            select substring(reverse(t.oct), v.number, 1) * power(8, v.number-1) val
              from master..spt_values v
             where v.type='p' and v.number between 1 and len(t.oct)
           ) x
       ) intVal
  from @t t;

Results

oct        intVal
---------- -----------
7101       3649
6          6
110111     36937