The number of differences in a column

Question

I would like to retrieve a column of how many differences in letters in each row. For instance

If you have a a value \"test\" and another row has a value \"testing \", t

Answer 1

I think you just want len() and lead():

select t.id, t.value, t.category,
       (len(lead(value) over (partition by t.category order by t.id) -
        len(value)
       ) as difference
from t;