int1?

**Shridhar Daithankar** · Nov 12 '05, 12:10 AM

Re: int1?

CSN wrote:
[color=blue]
> Is there any date type that can be used for 0-255
> values? Like an "int1" or byte column.[/color]

You can use a smallint with constraint.

HTH

Shridhar

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**Ron Johnson** · Nov 12 '05, 12:10 AM

Re: int1?

On Thu, 2003-10-09 at 02:16, CSN wrote:[color=blue]
> Is there any date type that can be used for 0-255
> values? Like an "int1" or byte column.[/color]

An int2 with a constraint on it.

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-----------------------------------------------------------------
Ron Johnson, Jr. ron.l.johnson@c ox.net
Jefferson, LA USA

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**Sean Chittenden** · Nov 12 '05, 12:10 AM

Re: int1?

> Is there any date type that can be used for 0-255[color=blue]
> values? Like an "int1" or byte column.[/color]

A SMALLINT is two bytes on disk, use "char" instead. This is a hidden
goodie in PostgreSQL and one that I wish was exposed via a more
conventional syntax (*hint hint*).

http://developer.postgresql.org/docs/postgres/datatype-character.html#DATATYPE-CHARACTER-SPECIAL-TABLE

-sc

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**Ron Johnson** · Nov 12 '05, 12:11 AM

Re: int1?

On Thu, 2003-10-09 at 03:19, Sean Chittenden wrote:[color=blue][color=green]
> > Is there any date type that can be used for 0-255
> > values? Like an "int1" or byte column.[/color]
>
> A SMALLINT is two bytes on disk, use "char" instead. This is a hidden
> goodie in PostgreSQL and one that I wish was exposed via a more
> conventional syntax (*hint hint*).
>
> http://developer.postgresql.org/docs...-SPECIAL-TABLE[/color]

Wouldn't that be, though, a signed byte? The OP wants unsigned.

--
-----------------------------------------------------------------
Ron Johnson, Jr. ron.l.johnson@c ox.net
Jefferson, LA USA

The purpose of the military isn't to pay your college tuition or
give you a little extra income; it's to "kill people and break
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**Karsten Hilbert** · Nov 12 '05, 12:11 AM

Re: int1?

> http://developer.postgresql.org/docs...-SPECIAL-TABLE
Is it unsafe practice to use the datatype "name" for
attributes that hold table or column names etc ?

Karsten
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**Stephan Szabo** · Nov 12 '05, 12:11 AM

Re: int1?

On Thu, 9 Oct 2003, Sean Chittenden wrote:
[color=blue][color=green]
> > Is there any date type that can be used for 0-255
> > values? Like an "int1" or byte column.[/color]
>
> A SMALLINT is two bytes on disk, use "char" instead. This is a hidden[/color]

However "char" has some serious deficiencies IIRC, such as the fact that
there's no int<->"char" casts and it's standard I/O format is characters.
You can use ascii and chr to get around some of that, but it's ugly.
[color=blue]
> goodie in PostgreSQL and one that I wish was exposed via a more
> conventional syntax (*hint hint*).[/color]

If we were going to do that I think we'd be better off making a new type
and leaving "char" alone.

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**Sean Chittenden** · Nov 12 '05, 12:11 AM

Re: int1?

> > > Is there any date type that can be used for 0-255 values? Like[color=blue][color=green][color=darkred]
> > > an "int1" or byte column.[/color]
> >
> > A SMALLINT is two bytes on disk, use "char" instead. This is a hidden[/color]
>
> However "char" has some serious deficiencies IIRC, such as the fact
> that there's no int<->"char" casts and it's standard I/O format is
> characters. You can use ascii and chr to get around some of that,
> but it's ugly.[/color]

*nods* I have explicit casts everywhere when dealing with "char" and
it's far from being elegant or clean.
[color=blue]
>[color=green]
> > goodie in PostgreSQL and one that I wish was exposed via a more
> > conventional syntax (*hint hint*).[/color]
>
> If we were going to do that I think we'd be better off making a new
> type and leaving "char" alone.
>[/color]

You won't hear any disagreements from me on this one. I've
sufficiently abused "char" as a 1 byte storage field and would love to
see an int1 or tinyint datatype added to cover this situation. -sc

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Sean Chittenden

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**Ron Johnson** · Nov 12 '05, 12:11 AM

Domains (was Re: int1?)

On Thu, 2003-10-09 at 12:54, Sean Chittenden wrote:[color=blue][color=green][color=darkred]
> > > > Is there any date type that can be used for 0-255 values? Like
> > > > an "int1" or byte column.
> > >
> > > A SMALLINT is two bytes on disk, use "char" instead. This is a hidden[/color]
> >
> > However "char" has some serious deficiencies IIRC, such as the fact
> > that there's no int<->"char" casts and it's standard I/O format is
> > characters. You can use ascii and chr to get around some of that,
> > but it's ugly.[/color]
>
> *nods* I have explicit casts everywhere when dealing with "char" and
> it's far from being elegant or clean.
>[color=green]
> >[color=darkred]
> > > goodie in PostgreSQL and one that I wish was exposed via a more
> > > conventional syntax (*hint hint*).[/color]
> >
> > If we were going to do that I think we'd be better off making a new
> > type and leaving "char" alone.
> >[/color]
>
> You won't hear any disagreements from me on this one. I've
> sufficiently abused "char" as a 1 byte storage field and would love to
> see an int1 or tinyint datatype added to cover this situation. -sc[/color]

CREATE DOMAIN

http://www.postgresql.org/docs/7.3/static/sql-createdomain.html

CREATE DOMAIN domainname [AS] data_type
[ DEFAULT default_expr ]
[ constraint [, ... ] ]

where constraint is:

[ CONSTRAINT constraint_name ]
{ NOT NULL | NULL }

test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
ERROR: DefineDomain: CHECK Constraints not supported

So, how would I create a domain that limits a smallint?

--
-----------------------------------------------------------------
Ron Johnson, Jr. ron.l.johnson@c ox.net
Jefferson, LA USA

"You can either have software quality or you can have pointer
arithmetic, but you cannot have both at the same time."
Bertrand Meyer

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**Bruno Wolff III** · Nov 12 '05, 12:11 AM

Re: Domains (was Re: int1?)

On Thu, Oct 09, 2003 at 14:28:57 -0500,
Ron Johnson <ron.l.johnson@ cox.net> wrote:[color=blue]
>
> http://www.postgresql.org/docs/7.3/s...atedomain.html
> CREATE DOMAIN domainname [AS] data_type
> [ DEFAULT default_expr ]
> [ constraint [, ... ] ]
>
> where constraint is:
>
> [ CONSTRAINT constraint_name ]
> { NOT NULL | NULL }
>
> test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
> ERROR: DefineDomain: CHECK Constraints not supported
>
> So, how would I create a domain that limits a smallint?[/color]

You need to use 7.4. In 7.3 you couldn't use check constraints with domains.

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**Ron Johnson** · Nov 12 '05, 12:12 AM

Re: Domains (was Re: int1?)

On Thu, 2003-10-09 at 14:46, Bruno Wolff III wrote:[color=blue]
> On Thu, Oct 09, 2003 at 14:28:57 -0500,
> Ron Johnson <ron.l.johnson@ cox.net> wrote:[color=green]
> >
> > http://www.postgresql.org/docs/7.3/s...atedomain.html
> > CREATE DOMAIN domainname [AS] data_type
> > [ DEFAULT default_expr ]
> > [ constraint [, ... ] ]
> >
> > where constraint is:
> >
> > [ CONSTRAINT constraint_name ]
> > { NOT NULL | NULL }
> >
> > test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
> > ERROR: DefineDomain: CHECK Constraints not supported
> >
> > So, how would I create a domain that limits a smallint?[/color]
>
> You need to use 7.4. In 7.3 you couldn't use check constraints with domains.[/color]

So is there a documentation "bug", or, what kind of constraints
can be placed on domains besides { NOT NULL | NULL }?

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Ron Johnson, Jr. ron.l.johnson@c ox.net
Jefferson, LA USA

Causation does NOT equal correlation !!!!!!!!

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**Peter Eisentraut** · Nov 12 '05, 12:12 AM

Re: Domains (was Re: int1?)

Ron Johnson writes:
[color=blue]
> test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
> ERROR: DefineDomain: CHECK Constraints not supported
>
> So, how would I create a domain that limits a smallint?[/color]

You would have to wait for PostgreSQL 7.4.

--
Peter Eisentraut peter_e@gmx.net

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**Bruno Wolff III** · Nov 12 '05, 12:12 AM

Re: Domains (was Re: int1?)

On Thu, Oct 09, 2003 at 14:46:08 -0500,
Ron Johnson <ron.l.johnson@ cox.net> wrote:[color=blue]
> On Thu, 2003-10-09 at 14:46, Bruno Wolff III wrote:[color=green]
> > On Thu, Oct 09, 2003 at 14:28:57 -0500,
> > Ron Johnson <ron.l.johnson@ cox.net> wrote:[color=darkred]
> > >
> > > http://www.postgresql.org/docs/7.3/s...atedomain.html
> > > CREATE DOMAIN domainname [AS] data_type
> > > [ DEFAULT default_expr ]
> > > [ constraint [, ... ] ]
> > >
> > > where constraint is:
> > >
> > > [ CONSTRAINT constraint_name ]
> > > { NOT NULL | NULL }
> > >
> > > test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
> > > ERROR: DefineDomain: CHECK Constraints not supported
> > >
> > > So, how would I create a domain that limits a smallint?[/color]
> >
> > You need to use 7.4. In 7.3 you couldn't use check constraints with domains.[/color]
>
> So is there a documentation "bug", or, what kind of constraints
> can be placed on domains besides { NOT NULL | NULL }?[/color]

I think the documentation is correct. As I read it it says that only NOT NULL
and NULL constraints are allowed. This is easy to overlook. I know I got
caught by this when I tried it.

I started using 7.4 pretty early on since I wanted to use check constraints
in earthdistance to have a domain that represented points on the surface of
the earth on top of the cube data type.

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**Ron Johnson** · Nov 12 '05, 12:12 AM

Re: Domains (was Re: int1?)

On Thu, 2003-10-09 at 15:13, Bruno Wolff III wrote:[color=blue]
> On Thu, Oct 09, 2003 at 14:46:08 -0500,
> Ron Johnson <ron.l.johnson@ cox.net> wrote:[color=green]
> > On Thu, 2003-10-09 at 14:46, Bruno Wolff III wrote:[color=darkred]
> > > On Thu, Oct 09, 2003 at 14:28:57 -0500,
> > > Ron Johnson <ron.l.johnson@ cox.net> wrote:
> > > >
> > > > http://www.postgresql.org/docs/7.3/s...atedomain.html
> > > > CREATE DOMAIN domainname [AS] data_type
> > > > [ DEFAULT default_expr ]
> > > > [ constraint [, ... ] ]
> > > >
> > > > where constraint is:
> > > >
> > > > [ CONSTRAINT constraint_name ]
> > > > { NOT NULL | NULL }
> > > >
> > > > test1=# create domain d_tinyint as smallint constraint chk_tinyint CHECK (smallint between 0 and 255);
> > > > ERROR: DefineDomain: CHECK Constraints not supported
> > > >
> > > > So, how would I create a domain that limits a smallint?
> > >
> > > You need to use 7.4. In 7.3 you couldn't use check constraints with domains.[/color]
> >
> > So is there a documentation "bug", or, what kind of constraints
> > can be placed on domains besides { NOT NULL | NULL }?[/color]
>
> I think the documentation is correct. As I read it it says that only NOT NULL
> and NULL constraints are allowed. This is easy to overlook. I know I got
> caught by this when I tried it.[/color]

test1=# create domain foo as smallint not null;
CREATE DOMAIN

test1=# create domain bar as smallint CONSTRAINT wiggle not null;
CREATE DOMAIN

Oh, ok. Stuff in [] is not necessary. Still confusing.

--
-----------------------------------------------------------------
Ron Johnson, Jr. ron.l.johnson@c ox.net
Jefferson, LA USA

The difference between drunken sailors and Congressmen is that
drunken sailors spend their own money.

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**Joe Conway** · Nov 12 '05, 12:12 AM

Re: int1?

Ron Johnson wrote:[color=blue]
> On Thu, 2003-10-09 at 02:16, CSN wrote:
>[color=green]
>>Is there any date type that can be used for 0-255
>>values? Like an "int1" or byte column.[/color]
>
> An int2 with a constraint on it.
>[/color]

You can use the data type "char" (with the quotes, and without a (n)
decoration). See:

PostgreSQL: Not Found

http://www.postgresql.org/docs/view.php?version=7.3&idoc=0&file=datatype-character.html

near the bottom of the page.

Joe

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