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I am trying to compare the values of 2 fields in my attribute table and update a 3rd field as a result. In the field calculator I have 

CASE  when (("Address")  like  ("COUNTYNAME" )) then 'Match'
else 'Error'
End

so for the following toy data examples I would get the result Match,Error,Error Address,COUNTYNAME

  • Smith, Smith County
  • Bob, Smith County
  • Jane, Bob County

I have also tried CASE when (("Address") IN ("COUNTYNAME" )) then

Are there any other ways to compare text values within QGIS?

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2 Answers 2

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1

You can do something like this to compare two fields together:

Case
When  "Address" in (left( "CountyNM", strpos("CountyNM", ' ')-1)) Then 'Match'
Else 'Error'
End

The strpos() function will return the index position of the first ' ' (space) character and the left() function "trims" the string before that position. The -1 is to ensure that the space will not be included when doing comparison.

Here is the output of the above expression:

enter image description here

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0

The correct syntax is :

CASE WHEN "Address" LIKE ('%' || COUNTYNAME|| '%') THEN 'Match' ELSE 'Error' END

for the LIKE fonction to work you need to concatenate (using '||' ) the '%' wildcard (replace 0 to n character) with your field name, also you could add some UPPER or LOWER to convert to all uppercase (or all lowercase) to avoid false negative

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3
  • Is that not comparing the value from Address with a stationary COUNTYNAME instead of comparing the values in row [x] of field Address with field COUNTYNAME Commented Apr 3, 2018 at 16:04
  • This should compare the value of row(x) of the Address field with the value of row(x) of the COUNTYNAME field . Commented Apr 3, 2018 at 16:19
  • 1
    There is no ' around COUNTYNAME so it's taken as a field name, if you want you could put " around the field name it will work the same... Commented Apr 3, 2018 at 16:21

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