Question

I have a database table that contains among other things partial postal codes. I’m trying to write a query that will take a postal code and find the row in the table that matches that code as close as possible. In the example below a Gold customer with postal code ‘A1A B2E’ would match the first row and a Bronze customer with the same postal code would match the third row

CUST_TYPE | POST_CODE | SHIPPING_SURCHARGE
------------------------------------------
Gold      | A1A       | 0.99
Gold      | A2A       | 1.01
Gold      | A         | 3.00
Bronze    | A         | 1.05
Silver    | A         | 1.02
Bronze    | B         | 1.07

In all cases the query would query by both the CUST_TYPE and the POST_CODE columns. I’d want the query to only return a single row containing the one row that best matches the postal code. So, if I query Gold and ‘A1AB2B’ I would want the first row (Gold, A1A, 0.99) to be returned not both the first and third rows

Answer 1

SQL-Server

SELECT TOP (1) 
    *
FROM yourTable     
WHERE CUST_TYPE = @cust_type
  AND POST_CODE = LEFT( @postal_code, LEN(POST_CODE) ) 
ORDER BY LEN(POST_CODE) DESC 

---

Oracle

(I can’t test now:)

SELECT 
    *
FROM 
  ( SELECT 
        *
    FROM yourTable     
    WHERE CUST_TYPE = @cust_type
      AND POST_CODE = SUBSTR( @postal_code, 1, LENGTH(POST_CODE) ) 
    ORDER BY LENGTH(POST_CODE) DESC 
  )
WHERE rownum = 1