Question

I have a table of ‘games’ with a different entry for each game like so:

gameID   internalName
1        game1
2        game 1
3        game 2
4        game2
5        game3

etc.

So, the problem is now that I want to combine cases where the game’s titles (with whitespace stripped) are identical. In other the row with gameID of 2 would be merged with 1, and removed.

In addition, I want to update any entries in other tables that are using the gameID as a foreign key, to point to the new key.

I know I can do something like so, to get a list of which titles have duplicates:

SELECT gameID, count(REPLACE(internalName, ' ', '')), internalName  FROM games GROUP BY REPLACE(internalName, ' ', '') HAVING count(REPLACE(internalName, ' ', ''))  > 1

However, that doesn’t really help me to achieve what I need to do.

Any help?

Answer 1

something like that could help you to start

select g1.gameID as toKeep, g2.gameID toEliminate
from games g1
inner join games g2 on replace(g1.internalName, ' ', '') = replace(g2.internalName, ' ', '')
where g1.gameID < g2.gameID

but if you have 3 items to merge, this won’t work that well…

see http://sqlfiddle.com/#!2/fb294/6

but within a stored procedure or in php (or other language), you should be able to get what you want with that.

BETTER

with this one, even 3, or 4, or 5 identical result will work

select g1.gameID as toKeep, g2.gameID toEliminate
from games g1
inner join games g2 on replace(g1.internalName, ' ', '') = replace(g2.internalName, ' ', '')
where g1.gameID < g2.gameID
and g1.gameID not in (SELECT g4.gameID
                      from games g4
                      inner join games g3 on replace(g3.internalName, ' ', '') = replace(g4.internalName, ' ', '')
                      where g3.gameID < g4.gameID)

http://sqlfiddle.com/#!2/8fb21/1

EDIT : an example of (untested) stored procedure

CREATE PROCEDURE CLEANGAMENAMES()
BEGIN
  DECLARE toKeep, toEliminate INT;
  DECLARE cur1 CURSOR FOR 
    SELECT g1.gameID AS toKeep, g2.gameID AS toEliminate
    FROM games g1
    INNER JOIN games g2 ON REPLACE(g1.internalName, ' ', '') = REPLACE(g2.internalName, ' ', '')
    WHERE g1.gameID < g2.gameID
    AND g1.gameID NOT IN (SELECT g4.gameID
                          FROM games g4
                          INNER JOIN games g3 ON REPLACE(g3.internalName, ' ', '') = REPLACE(g4.internalName, ' ', '')
                          WHERE g3.gameID < g4.gameID)

  OPEN cur1;

  read_loop: LOOP
    FETCH cur1 INTO toKeep, toEliminate;
    UPDATE <anyTable> set gameId = toKeep where gameId = toEliminate;
    -- as many tables as you need
    DELETE FROM games where gameID = toEliminate;
    UPDATE games set internalName = REPLACE(internalName, ' ', '');

  END LOOP;

  CLOSE cur1;
END;