I am new to QGIS. This question about how to use the field calculator, because the procedure to replace all fields is explained very nicely in Replacing all null values from attribute table with zeros using QGIS?

I have the null features selected, but now I am struggling to find a means to change all of them to "no" instead of the "0".

Can someone help?

  • do you have a text field or a numeric field ? – radouxju Nov 27 '18 at 8:44
  • I am not sure. How can I find out? – Papayapap Nov 27 '18 at 8:54
  • QGIS 3 : right click on layer > properties > identify icon (i in blue circle), then scroll to fields and you will see the type of field. – radouxju Nov 27 '18 at 9:05
  • okay, it is string, yes. – Papayapap Nov 27 '18 at 9:06
  • have you tried with 'no' in the field calculator ? – radouxju Nov 27 '18 at 9:10

Update your column using the following "code" in the field calculator

CASE WHEN "field" IS NULL THEN 'no' ELSE "field" END

This doesn't even need you to select all NULL-values beforehand - and requires your column to not to be of any numerical data type.

  • 2
    Alternative: if( "field" IS NULL, 'no', "field"). Yours is of course more descriptive. :) – Stefan Nov 27 '18 at 8:46
  • Thanks Erik and Stefan, and for the "field" I should put the name of my variable without the quotations, yes? – Papayapap Nov 27 '18 at 8:50
  • 1
    I usually use CASE WHEN because I find it easier to nest. – Erik Nov 27 '18 at 8:50
  • "field" is you columns name - and you have to use the quotation marks. Column names are always refered to by double quotation marks, values (especially strings) by single quotation marks. – Erik Nov 27 '18 at 8:52
  • That's good to know, thanks. For me the code doesn't work. I put it in the field calculator, replaced the column name, and checked the "update existing field option" but when I click on "ok" nothing happens. Do you have an idea what is happening? – Papayapap Nov 27 '18 at 9:01

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