Re: [libreoffice-users] Base query - CONCAT function

On Sat, 2017-09-16 at 18:37 +0200, Harvey Nimmo wrote:
> On Sat, 2017-09-16 at 18:31 +0200, Robert Großkopf wrote:
> > Hi Harvey,
> > > But shouldn't the CONCAT( ' & ', [Partnervorname] ), '' )
> > > actually
> > > return a NULL due to the '' (i.e. not a space, zero length)?
> >
> > NULL: There is nothing inside, no string, no number, no data ...
> > Empty: Could only be for strings - nothing to see, but its a string
> > with
> > zero length.
> >
> > Base will save for default all fields without content as NULL, not
> > as
> > fields, which are empty. The difference: You could concatenate
> > empty
> > fields with content of other fields without problems, because it
> > recognizes an empty string. With NULL it won't work.
> >
> > The Help in LibreOffice and the GUI is missleading here, because
> > Base
> > won't save fields as empty fields but as NULL.
> >
> > Regards
> >
> > Robert
> >  
>
> Thanks, Robert. I had a feeling that would be the answer. Many thanks
> for helping me to clear that up. Your proposed syntax is certainly
> more
> economical than the COALESCE alternative.
>
> Cheers
> Harvey

Hi Robert,
....but as I now have discovered, the COALESCE command is the correct
solution to cope with several alternative syntax combinations by
concatenation. Each CONCAT expression in the COALESCE parameter list
can represent one of the desired syntax combinations, always assuming
that the successive expressions in the parameter list can 'disqualify'
themselves by returning a NULL from CONCAT before reaching the desired
combination. It strikes me as being quite an elegant solution.

Many thanks for your help.

Cheers
Harvey


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