-- Database schema
| AREA_CODE_STATE : area_code [ INT ] primary_key , state [ TEXT ] | CONTESTANTS : contestant_number [ INT ] primary_key , contestant_name [ TEXT ] | VOTES : vote_id [ INT ] primary_key , phone_number [ INT ] , state [ TEXT ] VOTES.state = AREA_CODE_STATE.state , contestant_number [ INT ] VOTES.contestant_number = CONTESTANTS.contestant_number , created [ TEXT ] |
-- -- List the area codes in which voters voted both for the contestant 'Tabatha Gehling' and the contestant 'Kelly Clauss'.

SELECT T3.area_code FROM contestants AS T1 JOIN votes AS T2 ON T1.contestant_number  =  T2.contestant_number JOIN area_code_state AS T3 ON T2.state  =  T3.state WHERE T1.contestant_name  =  'Tabatha Gehling' INTERSECT SELECT T3.area_code FROM contestants AS T1 JOIN votes AS T2 ON T1.contestant_number  =  T2.contestant_number JOIN area_code_state AS T3 ON T2.state  =  T3.state WHERE T1.contestant_name  =  'Kelly Clauss';