user: Question: How many channels are there in the Greater Tokyo area?
Columns: ['Channel', 'Channel name', 'Callsign', 'Signal power', 'Broadcast area']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'NHK General TV / NHK G (GTV)', 'JOAK-DTV', '10kW', 'Greater Tokyo']
SQL:

assistant: SELECT COUNT("Channel") FROM "Table" WHERE "Broadcast area" = 'Greater Tokyo';