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To find and replace all null values in a specific column I am using:

case when "myColumn" is NULL then '99999999' else "myColumn" end

But how can I use the QGIS calculator to find and replace all null values in the multiple columns?

  • Do I understand correct: You want to execute the query (which you say is working as expected) for all columns of a layer? – Matthias Kuhn Sep 11 '13 at 9:12
  • I'm going to be a big old meanie here, and ask: are you sure you would ever want to do that? Using VERY_LARGE_NUM for unknown or invalid values is an old Fortran thing, and is used only by languages/systems which don't handle nulls properly. Could there ever be a time when you already legitimately had the value 99999999 in a column? Also, it's important that Null≠Null, but 99999999==99999999, so testing for unknowns will no longer work. If this is for output, dump to CSV and sed null to 99999999. Srsly; drop the P-38, can of worms ahead… – scruss Sep 11 '13 at 13:14
  • matthias Kuhn - yes thats is correct – Bwyss Sep 12 '13 at 7:25
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That is currently not possible automatically in Field Calculator because these calculations can only affect one column.

Solutions would require python scripting.

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You could always open the dbf-file (assuming you are working with a shape-file) directly in e.g. Open Office Calc (Excel doesn't handle dbf without problems...), select the columns of interest, and then run a simple find/replace within the selected columns.

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