gistfile1.sql

mysql> select 'Krąków, Poland';
+------------------+
| Krąków, Poland   |
+------------------+
| Krąków, Poland   |
+------------------+

mysql> select binary 'Krąków, Poland';
+---------------------------+
| binary 'Krąków, Poland'   |
+---------------------------+
| Krąków, Poland            |
+---------------------------+

mysql> select 'Krąków, Poland' = binary 'Krąków, Poland';
+------------------------------------------------+
| 'Krąków, Poland' = binary 'Krąków, Poland'     |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+

-- This is the query Rails executes when validating `validates :address, uniqueness: true`
mysql> SELECT 1 AS one FROM `locations` WHERE `locations`.`address` = BINARY 'Krąków, Poland';
Empty set (0.00 sec)

mysql> SELECT 1 AS one FROM `locations` WHERE `locations`.`address` = 'Krąków, Poland';
+-----+
| one |
+-----+
|   1 |
+-----+