user: Question: Name the service for 7th Marines rank of Sergeant
Columns: ['Name', 'Service', 'Rank', 'Place of action', 'Unit']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Smedley Butler Category:Articles with hCards', 'Marine Corps', 'Major', 'Fort Riviere , Haiti', '2nd Marines']
SQL:

assistant: SELECT "Service" FROM "Table" WHERE "Unit" = '7th Marines' AND "Rank" = 'Sergeant';