[Qgis-user] SQL to update table
Brent Wood
pcreso at pcreso.com
Sat Mar 14 16:25:45 PDT 2015
"NULL" means unknown, so you can't say if another value = NULL, it may or may not - the db can't tell.
Instead of "=" there is usually an "isnull" or "is null" operator in your database to test for null,
in your case, try:update "mc-roadsegs" Set "RFROMHN" = "" Where "RFROMHN" is null;
(I use Postgis rather than Spatialite, which would use ' instead of " to define strings, so:update "mc-roadsegs" Set "RFROMHN" = '' Where "RFROMHN" is null;)
HTH,
Brent Wood
From: Chuck Young <wylie1066 at gmail.com>
To: Qgis-user at lists.osgeo.org
Sent: Sunday, March 15, 2015 10:57 AM
Subject: [Qgis-user] SQL to update table
I am trying to eliminate the text "NULL" from a table. I have imported a set of Tiger road data and in some of the columns that I need to display the data itr has "NULL" in the field. If it is Null I would really like that NOT to show up in the labeling on the map.
I have tried some standard SQL update queries but they didn't work.
I tried the following from the QSpatialite form that appears from within QGIS.
Example:
update "mc-roadsegs" Set "RFROMHN" = "" Where "RFROMHN" = "NULL";
I also tried to construct a query from within the query builf=der at the top of the Attribute table in Edit mode.
I really need to remove these unwanted valued. It has been a while since I used SQL on a routine basis so I am a bit rusty.
Any help will be much appreciated!
Thanks
Chuck
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