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Question

Hi,
This question might have been asked before but I don't know how to describe it in the search field.
There are 3 records with 2 fields (id, name). These records are:
1,Amsterdam
2,Amster
3,Am
I want to find the record that holds the most possible information:
searching Amsterdam must return 1; searching Amsterdamned must return 1; searching America must return 3; searching United must return 0 (or null).
So the logic is to search for the whole string and return the id when found. If not found remove the most right character and search until found or a empty string.
Since this logic has to be a part of SQL I wonder if there is a smart way (without writing a PL/SQL function) to solve this?
I'm curious.
Geert.

Answer 1

Hi, Geert,
So you're only interested in strings that start the same way? That is, the fact that 'Amsterdam' and 'United' have the substring 'te' in common doesn't matter, because 'te' comes in the middle of those strings.
If that's so, you can use LIKE to compare the strings.
WITH   got_r_num    AS
     SELECT     p.place_name
     ,     a.place_id
     ,     a.place_name     AS a_place_name          -- Not needed, nut may be nice
     ,     RANK () OVER ( PARTITION BY  p.place_name
                           ORDER BY          LENGTH (a.place_name)  DESC
                    )  AS r_num
     FROM          possible_places  p
     LEFT OUTER JOIN      actual_places       a  ON  p.place_name LIKE a.place_name || '%'
SELECT       place_name
,       NVL (place_id, 0)     AS place_id     -- or, if you want NULL, just place_id
,       a_place_name                       -- if wanted
FROM       got_r_num
WHERE       r_num     = 1
ORDER BY  place_name
;Whenever you have a problem, please post CREATE TABLE and INSERT statments for some sample data, like this:
CREATE TABLE     actual_places
(   place_id     NUMBER (6)     PRIMARY KEY
,   place_name     VARCHAR2 (20)     
INSERT INTO actual_places (place_id, place_name) VALUES (1,  'Amsterdam');
INSERT INTO actual_places (place_id, place_name) VALUES (2,  'Amster');
INSERT INTO actual_places (place_id, place_name) VALUES (3,  'Am');
CREATE TABLE     possible_places
(   place_name     VARCHAR2 (20)     PRIMARY KEY
INSERT INTO possible_places (place_name) VALUES ('Amsterdam');
INSERT INTO possible_places (place_name) VALUES ('Amsterdamned');
INSERT INTO possible_places (place_name) VALUES ('America');
INSERT INTO possible_places (place_name) VALUES ('United');Also, post the results you want from that data, exactly as you want to see them. The query above produces this output:
PLACE_NAME             PLACE_ID A_PLACE_NAME
America                       3 Am
Amsterdam                     1 Amsterdam
Amsterdamned                  1 Amsterdam
United                        0See the forum FAQ {message:id=9360002}