[Info-ingres] Question on min() and nullability

[Adrian Williamson]

I was more curious about WTF ii_dv_desc was all about:

 



 

But I then found this:

 

http://www.databaseteam.org/10-database/7ae0587cf0276f06.htm

 

 

 

 

-----Original Message-----
From: info-ingres-bounces at lists.planetingres.org <info-ingres-bounces at lists.planetingres.org> On Behalf Of Martin Bowes
Sent: 29 October 2020 13:14
To: Karl Schendel <schendel at kbcomputer.com>
Cc: info-ingres at lists.planetingres.org
Subject: Re: [Info-ingres] Question on min() and nullability

 

Of course, thanks Karl.

 

-----Original Message-----

From: Karl Schendel < <mailto:schendel at kbcomputer.com> schendel at kbcomputer.com> 

Sent: 29 October 2020 13:11

To: Martin Bowes < <mailto:martin.bowes at ndph.ox.ac.uk> martin.bowes at ndph.ox.ac.uk>

Cc:  <mailto:info-ingres at lists.planetingres.org> info-ingres at lists.planetingres.org

Subject: Re: [Info-ingres] Question on min() and nullability

 

 

 

> On Oct 29, 2020, at 9:08 AM, Martin Bowes < <mailto:martin.bowes at ndph.ox.ac.uk> martin.bowes at ndph.ox.ac.uk> wrote:

> 

> select ii_dv_desc(min(a)) from session.test Executing . . .

>  

>  

> ┌──────────────────────────────────────────────────────────────┐

> │col1                                                          │

> ├──────────────────────────────────────────────────────────────┤

> │nullable ingresdate                                           │

> └──────────────────────────────────────────────────────────────┘

> (1 row)

>  

> How can the min of a non nullable field ever itself be a null?

>  

 

Because it's an aggregate.  min can be null if there are no rows.

 

Karl

 

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