How to create new columns in QGIS by writng Conditional query on other columns of attributes table

Question

First of all, sorry, I couldn't phrase my question better.

So I want to be able to add a new column in my attributes table, say B, and it's value should be 1 if Column A's value is 1 and 0 if Column A's value is 2. in other words:

If A==1 : B=1

elif A==2 : B=2 I couldn't figure out a way to do this using Field Calculator.

Thanks

Answer 1

You can use a case statement to do that:

CASE 
    WHEN "A" = 1 THEN 1 
    WHEN "A" = 2 THEN 2 
END

If you want everything else to match you can use ELSE

CASE 
    WHEN "A" = 1 THEN 1 
    WHEN "A" = 2 THEN 2
    ELSE 0
END

This way everything that is not A=1 or A=2 will get assigned 0.