SELECT id, haslo, znaczenie, data FROM sennik WHERE  (haslo LIKE 'S%' OR haslo LIKE 's%' OR haslo LIKE 'Ś%' OR haslo LIKE 'ś%' ) ORDER BY haslo ASC

Illegal mix of collations (latin2_general_ci,IMPLICIT) and (latin1_swedish_ci,COERCIBLE) for operation 'like'