Hi Matthias and Jürgen,
Thanks for your clarifications. Now it makes more sense and I agree that
the Concat version is easier to use.
Andreas
On 21.09.2015 10:26, Matthias Kuhn wrote:
To clarify with a more meaningful example, the following two
expressions are equal
* CONCAT( name, ', ', country )
* COALESCE( name, '' ) || ', ' || COALESCE( country, '' )
Example:
Given features with the attributes:
* Feature 1:
name : 'Tokyo'
country: 'Japan'
* Feature 2:
name: 'Atlantis'
country: NULL
The result is for both methods:
* Feature1: 'Tokyo, Japan'
* Feature2: ', Atlantis'
PS: thanks for the hint with the quotes, I was to quick on the send button
Best regards,
Matthias
On 09/21/2015 08:39 AM, Andreas Neumann wrote:
Hi,
So how is concat(NULL,fieldname) any better than
COALESCE(fieldname,''). To me it is the same complexity and not
really an improvement. But maybe I don't get it. The only slight
advantage would be that "concat" may be a more familiar term than
coalesce. But if you come from a database background you already know
COALESCE. Any serious GIS professional needs to know databases.
Another small thing:
Do not mix up double quotes (") and single quotes ('). Whenever you
use a string, do use single quotes, when you use an attribute either
use no quotes or double quotes for some providers if you use capital
letters in field names (which is discourage anyway).
Andreas
On 20.09.2015 12:59, Matthias Kuhn wrote:
Hi Phil,
In addition to COALESCE I'd like to promote the use of the function
*CONCAT()* which treats NULL values as empty strings (it was changed
recently, it's probably since 2.10) what makes it very handy.
Example:
NULL || "hello" -> NULL
vs.
CONCAT( NULL , "hello") -> "hello
vs.
COALESCE( NULL, "" ) || "hello" -> "hello"
Cheers,
Matthias
On 09/20/2015 09:54 AM, Phil (The Geek) Wyatt wrote:
Hi Folks,
I am working with LIST Address Points data from
http://listdata.thelist.tas.gov.au/opendata/ (Specifically Clarence
Municipality) and I need to concatenate into one field the full
address of each location. I am struggling to figure out how to do
it when there are fields for unit numbers, building names, numbers
to and from etc. Many of the fields are also NULL so clearly I want
those fields disregarded.
Can someone give me a quick heads up on how to NOT add the data
from a field that has NULL?
Chances are I will be doing this regularly so I am keen to document
the required expressions for others to use as well.
Cheers - Phil
Volunteer Mapper - Red Cross
<http://www.redcross.org.au/volunteering.aspx>
_______________________________________________
Qgis-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-user
_______________________________________________
Qgis-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-user
_______________________________________________
Qgis-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-user
_______________________________________________
Qgis-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-user
_______________________________________________
Qgis-user mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-user
