Selecting features and create new field with QGIS Field Calculator

Question

For example, Column A (1, Michigan Street, Michigan), Column B (Michigan Street) and Column C (Yes, No).

I want to use Field Calculator to update Column C in a way that it return NO if Column A contains the same street name as Column B. However, it does not work. What I tried:

Case
when "Column A" LIKE '%"Column B"%' then 'No'
else 'Yes'
end

So I try to go longer route by selecting features in Column A if it has exact words in Column B

"Column A" LIKE '%Column B%'

but it doesn't work either. Any idea on what expression to use as I don't want to write every code differently according to Column B?

Answer 1

The proper syntax is :

Case
when "Column A" LIKE '%' || "Column B" || '%' then 'No'
else 'Yes'
end

(You need to concatenate the column content with the '%' using the pipe operator)

Of course you also could use the alternative expression provided by @Babel

Answer 2

Use this expression:

case 
    when regexp_match ("Column A", "Column B") > 0
    then 'No'
    else 'Yes'
end

The function regexp_match() looks if the string of "Column B" is contained inside "Column A". It returns the position of the first character and 0 if the string is not found.