null values in a view

try:

CREATE OR REPLACE VIEW view1 AS
SELECT
name as a1,
null::text as a2,
'test'::text as a3
FROM
some_table;

Στις Wednesday 05 October 2011 17:22:21 ο/η Lauri Kajan έγραψε:

Hi all,

How could I create a view that returns null values among all other values.
Here is a sample that i want to achieve:

CREATE VIEW view1 AS
SELECT
attribute1 as a1,
null as a2
FROM
table;

Now the problem is that I got an warning: column "a2" has type "unknown"
I know that I should define a data type for a field a2. But how?
This works with other values but not with nulls:

CREATE VIEW view1 AS
SELECT
attribute1 as a1,
text null as a2,
text 'test' as a3
FROM
table;

Thanks

-Lauri Kajan

--
Achilleas Mantzios

On Wed, Oct 05, 2011 at 05:22:21PM +0300, Lauri Kajan wrote:

Hi all,

How could I create a view that returns null values among all other values.
Here is a sample that i want to achieve:

CREATE VIEW view1 AS
SELECT
attribute1 as a1,
null as a2
FROM
table;

Now the problem is that I got an warning: column "a2" has type "unknown"
I know that I should define a data type for a field a2. But how?

using normal cast:
null::text as a2

or cast(null as text);

Best regards,

depesz

--
The best thing about modern society is how easy it is to avoid contact with it.
http://depesz.com/

Lauri Kajan <lauri.kajan@gmail.com> writes:

This works with other values but not with nulls:

CREATE VIEW view1 AS
SELECT
attribute1 as a1,
text null as a2,
text 'test' as a3
FROM
table;

FYI, the syntax typename 'literal' works *only* with string literals,
not anything else. For any other target you have to write
CAST(value AS typename) or equivalently value::typename.
CAST is SQL-standard, :: is a Postgres-ism.

regards, tom lane

This worked.
Thank you all!

I know the casting is quite basic operation but could this be added to
the CREATE VIEW documentation? Now there is only an example:
CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
The same syntax won't work with other type as Tom wrote.

-Lauri