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

[Martin Bowes]

Of course, thanks Karl.

-----Original Message-----
From: Karl Schendel <schendel at kbcomputer.com> 
Sent: 29 October 2020 13:11
To: Martin Bowes <martin.bowes at ndph.ox.ac.uk>
Cc: 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 <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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