Re: cast bit to boolean?

On Thu, 3 May 2001, Vivek Khera wrote:

> How might one case a BIT to a BOOLEAN?  For example, I want to return
> rows which have non-zero bit representation for, say, (sel_a & b'0011').
> That is, rows with the first or second bit set.
>
> I tried an explicit CAST, and just the query directly, but the cast
> say you cant cast type 'bit' to 'bool', and the direct query says
> WHERE clause must return type bool, not type bit:
>
> create table t1 (sel_a BIT(6),sel_b BIT(6));
> insert into t1 values (b'000001',b'001000');
> select * from t1 where sel_a & b'100001';
> ERROR:  WHERE clause must return type bool, not type bit
>
> Where might I look for this?  The manual is quite sparse regarding BIT
> types.

There might be a better way, but you can write a conversion routine:

create function bool(bit) returns bool as '
begin
  if $1 = ''1''::bit
  then
    return true;
  end if;
  return false;
end;'
language 'plpgsql' with (isacachable);

should do the trick, albeit more slowly than a built-in or C function.

--
Joel Burton   <jburton@scw.org>
Director of Information Systems, Support Center of Washington