user: Question: What is the On-air ID with the frequency of 105.9, and purpose of Commercial?
Columns: ['Callsign', 'Area served', 'Frequency', 'Band', 'On-air ID', 'Purpose']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['2AAA', 'Wagga Wagga', '107.1', 'FM', '2AAA', 'Community']
SQL:

assistant: SELECT "On-air ID" FROM "Table" WHERE "Frequency" = '105.9' AND "Purpose" = 'Commercial';