O Michael Glaesemann έγραψε στις Jun 3, 2005 :
>
> On Jun 3, 2005, at 9:23 PM, Markus Bertheau β wrote:
>
> > This also bypasses the built in postgresql boolean literal parsing.
> >
> > I think casting from text to boolean should be possible, and use the
> > same algorithm that's used when casting from "unknown" to boolean.
>
> Actually, looking at the system tables, I don't think it is. There
> don't appear to be any casts to (or from) boolean. I may be looking
> at it wrong, but that's how it appears to me. Corrections, anyone?
>
> select type_source.typname as source, type_target.typname as target
> from pg_cast
> join pg_type type_source on (castsource = type_source.oid)
> join pg_type type_target on (casttarget = type_target.oid)
> where type_target.typname = 'bool'
> or type_source.typname = 'bool'
> order by type_source.typname;
>
> source | target
> --------+--------
> (0 rows)
>
> This is in v8.0.3
Also according to the docs:
http://www.postgresql.org/docs/current/static/datatype-boolean.html
"Tip: Values of the boolean type cannot be cast directly to other types
(e.g., CAST (boolval AS integer) does not work). This can be accomplished
using the CASE expression: CASE WHEN boolval THEN 'value if true' ELSE
'value if false' END."
I suppose the reverse must be true also.
>
> Michael Glaesemann
> grzm myrealbox com
>
> PS. Please don't top post.
>
>
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--
-Achilleus