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

You read a next record with LEAD. Then compare the strings with LIKE or other string functions:

select
  id, value, category,
  case when value like next_value + '%' or next_value like value + '%' 
       then len(next_value) - len(value)
  end as differences
from
(
  select id, value, category, lead(value) over (order by id) as next_value 
  from mytable
) this_and_next;

If you only want to compare values within the same category use a partition clause:

lead(value) over (partition by category order by id)

UPDATE: Please see DhruvJoshi's answer on SQL Server's LEN. This function doesn't count trailing blanks, as I assumed, so you need his trick in case you want to have them counted. Here is the doc on LEN confirming this behaviour: https://technet.microsoft.com/en-us/library/ms190329(v=sql.105).aspx