Q:

Conditional value in sqlite column

I have two integer columns in my sqlite table: a and b. I need to create a third column, c, which should contain either Y if a+b mod 2 == 1 or N if the previous condition is not satisfied.  I am not sure how to define such a column with a conditional value in my query. 

A:

You can do this readily in a query:
select a, b, (case when (a + b) % 2 = 1 then 'Y' else 'N' end) as col3
from table t;

You can do this in an update statement as well:
update t
    set col3 = (case when (a + b) % 2 = 1 then 'Y' else 'N' end) ;

You need to be sure that col3 exists.   You can do that with alter table:
alter table t add column col3 int;

