[GENERAL] null values in a view

[Lauri Kajan]

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

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Re: [GENERAL] null values in a view

[Achilleas Mantzios]

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
 



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Re: [GENERAL] null values in a view

[hubert depesz lubaczewski]

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

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Re: [GENERAL] null values in a view

[Tom Lane]

Lauri Kajan lauri.ka...@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

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Re: [GENERAL] null values in a view

[Lauri Kajan]

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

On Wed, Oct 5, 2011 at 5:39 PM, Tom Lane t...@sss.pgh.pa.us wrote:
 Lauri Kajan lauri.ka...@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


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