List the full names of Republican legislators who have a nickname.
full names refers to official_full_name; Republican refers to party = 'Republican'; nickname refers to nickname_name
SELECT T1.official_full_name FROM current AS T1 INNER JOIN `current-terms` AS T2 ON T1.bioguide_id = T2.bioguide WHERE T2.party = 'Republican' AND T1.nickname_name IS NOT NULL GROUP BY T1.official_full_name