Обсуждение: SELECT Field1 || Field2 FROM Table

Hello all,

I have PostgreSQL 7.1.1 installed on a RedHat 7.1 server.

When running the following query "SELECT Field1 || Field2 AS Result FROM Table"
the result is NULL when Field2 is NULL.

Same as if I use a PL/pgSQL function to concatenate Filed 1 || Field2.

Did I miss something?

Regards,
Jean-Michel POURE, pgAdmin development team

Yes, that's correct behaviour. Any operation on null will yield null.

What you need to do:
select coalesce(field1,'') || coalesce(field2,'') ...

-alex

On Wed, 13 Jun 2001, Jean-Michel POURE wrote:

> Hello all,
> 
> I have PostgreSQL 7.1.1 installed on a RedHat 7.1 server.
> 
> When running the following query "SELECT Field1 || Field2 AS Result FROM Table"
> the result is NULL when Field2 is NULL.
> 
> Same as if I use a PL/pgSQL function to concatenate Filed 1 || Field2.
> 
> Did I miss something?
> 
> Regards,
> Jean-Michel POURE, pgAdmin development team
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
> 
> 

Hello Robert (Bob?),

Thank you for your answer. I will surely make a wide use the COALESCE 
function in my scripts.
I also noticed the same behaviour in PL/pgSQL:

CREATE FUNCTION "xxxxxxxxxxxxxx" (text, text)
RETURNS text
AS 'BEGIN

RETURN $1 || ' ' || $2;
END;
'
LANGUAGE 'plpgsql'

Correct me if I am wrong:

It seems that a NULL value is not passed to the function ...
... or is it that a NULL value is not taken into account by PL/pgSQL.

Thank you all for the COALESCE trick.

Greetings from Jean-Michel POURE, Paris, France
pgAdmin development team

plpgsql is a bit tricky.

In 7.0, if an argument to a function was null, function did not execute at
all, and the result was assumed null.

In 7.1, you can control this behaviour by declaring function as 'strict'
or 'nostrict'. ex: create function(...) as '...' with (strict) gets old
behaviour, nostrict will do what you want.

On Thu, 14 Jun 2001, Jean-Michel POURE wrote:

> Hello Robert (Bob?),
> 
> Thank you for your answer. I will surely make a wide use the COALESCE 
> function in my scripts.
> I also noticed the same behaviour in PL/pgSQL:
> 
> CREATE FUNCTION "xxxxxxxxxxxxxx" (text, text)
> RETURNS text
> AS 'BEGIN
> 
> RETURN $1 || ' ' || $2;
> END;
> '
> LANGUAGE 'plpgsql'
> 
> Correct me if I am wrong:
> 
> It seems that a NULL value is not passed to the function ...
> ... or is it that a NULL value is not taken into account by PL/pgSQL.
> 
> Thank you all for the COALESCE trick.
> 
> Greetings from Jean-Michel POURE, Paris, France
> pgAdmin development team
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
> 
>