If you are using PHP / MySQL, Case sensitivity is set on the database end by the collation and character set that are selected when the table is created. The default character set and collation are latin1 and latin1_swedish_ci which are not case sensitive in string comparisons.
If you are using The MySQL GUI Tools for creating your table, go to the MySQL Administrator. In the Catalog section select you schema then double click the table that is being used by DataAssist to open the table editor. On the Table Options tab you can change the Character set and Collation.
More on case sensitivity in MySQL can be found here: