Hi,

there might be a better solution out there, but it seemed like an interesting 
problem so I wrote this function:

CREATE OR REPLACE FUNCTION stringdiff(text, text)
RETURNS TEXT
AS $$
    SELECT array_to_string(ARRAY(
        SELECT
            CASE WHEN substring($1 FROM n FOR 1) = substring($2 FROM n FOR 1)
                 THEN ' '
                 ELSE substring($2 FROM n FOR 1)
            END
        FROM generate_series(1, character_length($1)) as n), '');
$$ language sql;


Use it like this:
SELECT stringdiff('aaaaaaaaaa', 'axaaacaaza');

 stringdiff
------------
  x   c  z

Regards,
Aleksander


Peter Hunsberger wrote:
Can anyone give me a way to find the difference between two text
fields on a character by character basis.  Essentially,  I'd like to
logically AND the two together and for any position that has a
non-zero result show whatever character is in that position for the
second string.  The solution can be postgres specific but something
approaching ANSI SQL would also be helpful (if possible).


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