Split a MYSQL string from GROUP_CONCAT into an ( array, like, expression, list) that IN () can understand

Instead of using IN(), would using FIND_IN_SET() be an option too?

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_find-in-set

mysql> SELECT FIND_IN_SET('b','a,b,c,d');
    -> 2

---

Here's a full example based on the example problem in the question, confirmed as tested by the asker in an earlier edit to the question:

SELECT name FROM person LEFT JOIN tag ON person.id = tag.person_id GROUP BY person.id 
  HAVING ( FIND_IN_SET(1, GROUP_CONCAT(tag.tag_id)) ) AND ( FIND_IN_SET(2, GROUP_CONCAT(tag.tag_id)) );
+------+
| name |
+------+
| Bob  |
+------+

You can pass a string as array, using a split separator, and explode it in a function, that will work with the results.

For a trivial example, if you have a string array like this: 'one|two|tree|four|five', and want to know if two is in the array, you can do this way:

create function str_in_array( split_index varchar(10), arr_str varchar(200), compares varchar(20) )
  returns boolean
  begin
  declare resp boolean default 0;
  declare arr_data varchar(20);

  -- While the string is not empty
  while( length( arr_str ) > 0  ) do

  -- if the split index is in the string
  if( locate( split_index, arr_str ) ) then

      -- get the last data in the string
    set arr_data = ( select substring_index(arr_str, split_index, -1) );

    -- remove the last data in the string
    set arr_str = ( select
      replace(arr_str,
        concat(split_index,
          substring_index(arr_str, split_index, -1)
        )
      ,'')
    );
  --  if the split index is not in the string
  else
    -- get the unique data in the string
    set arr_data = arr_str;
    -- empties the string
    set arr_str = '';
  end if;

  -- in this trivial example, it returns if a string is in the array
  if arr_data = compares then
    set resp = 1;
  end if;

 end while;

return resp;
end
|

delimiter ;

I want to create a set of usefull mysql functions to work with this method. Anyone interested please contact me.

For more examples, visit http://blog.idealmind.com.br/mysql/how-to-use-string-as-array-in-mysql-and-work-with/