Обсуждение: How to cast VARCHAR to BYTEA and vice-versa?
Hello all, I have a table with a VARCHAR column that I need to convert to a BYTEA. How do I cast VARCHAR to BYTEA? The following doesn't seem to work as it yields the 'cannot cast varchar to bytea' error message: varchar_data::bytea On the same topic, how do I do the reverse, that is, how to I cast from BYTEA back to VARCHAR? Thanks, -Michael Moran
On Tue, 2005-03-08 at 07:31 -0800, Moran.Michael wrote: > Hello all, > > I have a table with a VARCHAR column that I need to convert to a BYTEA. > > How do I cast VARCHAR to BYTEA? have you looked at the encode() and decode() functions ? http://www.postgresql.org/docs/7.4/interactive/functions-string.html gnari
"Moran.Michael" wrote: > > Hello all, > > I have a table with a VARCHAR column that I need to convert to a BYTEA. > > How do I cast VARCHAR to BYTEA? > > The following doesn't seem to work as it yields the 'cannot cast varchar to > bytea' error message: > > varchar_data::bytea > > On the same topic, how do I do the reverse, that is, how to I cast from > BYTEA back to VARCHAR? > > Thanks, > -Michael Moran > > As far as I remember varchar_data::TEXT::BYTEA works. Vice versa dto. Be aware BYTEA data may contain character codes unconvertable to VARCHAR, especially '\0'. Regards, Christoph
Christoph, is that recent functionality? I'm running 7.4 and I get: ERROR: cannot cast type text to bytea I get similar errors when trying to go the other direction. On Mon, 14 Mar 2005 11:32:26 +0100, Christoph Haller <ch@rodos.fzk.de> wrote: > "Moran.Michael" wrote: > > > > Hello all, > > > > I have a table with a VARCHAR column that I need to convert to a BYTEA. > > > > How do I cast VARCHAR to BYTEA? > > > > The following doesn't seem to work as it yields the 'cannot cast varchar to > > bytea' error message: > > > > varchar_data::bytea > > > > On the same topic, how do I do the reverse, that is, how to I cast from > > BYTEA back to VARCHAR? > > > > Thanks, > > -Michael Moran > > > > > As far as I remember > varchar_data::TEXT::BYTEA > works. Vice versa dto. > Be aware BYTEA data may contain character codes > unconvertable to VARCHAR, especially '\0'. > > Regards, Christoph > > ---------------------------(end of broadcast)--------------------------- > TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq >
Seems my remembrance was wrong, ::TEXT::BYTEA causes
ERROR: cannot cast type text to bytea
on my 7.4.5 version too.
Looking into "Other Binary String Functions" within the manual,
sheds light on how to do it:
::TEXT::BYTEA
Function decode(string text, type text) Return Type bytea
select decode('123\\000456'::text, 'escape'); decode
------------123\000456
(1 row)
::BYTEA::TEXT
Function encode(string bytea, type text) Return Type text
select encode('123\\000456'::bytea, 'escape'); encode
------------123\000456
(1 row)
Sorry for the confusion I have caused,
especially because there already was a correct answer
sent by Ragnar.
Regards, Christoph
Lance Peterson wrote:
>
> Christoph, is that recent functionality? I'm running 7.4 and I get:
> ERROR: cannot cast type text to bytea
>
> I get similar errors when trying to go the other direction.
>
> On Mon, 14 Mar 2005 11:32:26 +0100, Christoph Haller <ch@rodos.fzk.de> wrote:
> > "Moran.Michael" wrote:
> > >
> > > Hello all,
> > >
> > > I have a table with a VARCHAR column that I need to convert to a BYTEA.
> > >
> > > How do I cast VARCHAR to BYTEA?
> > >
> > > The following doesn't seem to work as it yields the 'cannot cast varchar to
> > > bytea' error message:
> > >
> > > varchar_data::bytea
> > >
> > > On the same topic, how do I do the reverse, that is, how to I cast from
> > > BYTEA back to VARCHAR?
> > >
> > > Thanks,
> > > -Michael Moran
> > >
> > >
> > As far as I remember
> > varchar_data::TEXT::BYTEA
> > works. Vice versa dto.
> > Be aware BYTEA data may contain character codes
> > unconvertable to VARCHAR, especially '\0'.
> >
> > Regards, Christoph
> >