Question

Background

To replace invalid zip codes.

Sample Data

Consider the following data set:

 Typo  | City       | ST | Zip5
-------+------------+----+------
 33967 | Fort Myers | FL | 33902
 33967 | Fort Myers | FL | 33965
 33967 | Fort Myers | FL | 33911
 33967 | Fort Myers | FL | 33901
 33967 | Fort Myers | FL | 33907
 33967 | Fort Myers | FL | 33994
 34115 |Marco Island| FL | 34145
 34115 |Marco Island| FL | 34146
 86405 |  Kingman   | FL | 86404
 86405 |  Kingman   | FL | 86406

33967 closely matches 33965, although 33907 could also be correct. (In this case, 33967 is a valid zip code, but not in our zip code database.)

34115 closely matches is 34145 (off by one digit, with a difference of 3 for that digit).

86405 closely matches both.

Sometimes digits are simply reversed (e.g,. 89 instead of 98).

Question

How would you write a SQL statement that finds the “minimum distance” between multiple numbers that have the same number of digits, returning at most one result no matter what?

Ideas

• Subtract the digits.
• Use LIMIT 1.

Conditions

PostgreSQL 8.3

Answer 1

This sounds like a case for Levenshtein distance.

The Levenshtein distance between two
strings is defined as the minimum
number of edits needed to transform
one string into the other, with the
allowable edit operations being
insertion, deletion, or substitution
of a single character.

It looks like PostgreSQL has it built-in:

test=# SELECT levenshtein('GUMBO', 'GAMBOL');
 levenshtein
-------------
           2
(1 row)

http://www.postgresql.org/docs/8.3/static/fuzzystrmatch.html