user: Question: Competition of U.S Championships, and a Event of All Around has what average year?
Columns: ['Year', 'Competition', 'Location', 'Event', 'Final-Rank', 'Final-Score']
Types: ['real', 'text', 'text', 'text', 'real', 'real']
Sample row: [2006.0, 'U.S Championships', 'Saint Paul', 'All Around', 3.0, 59.65]
SQL:

assistant: SELECT AVG("Year") FROM "Table" WHERE "Competition" = 'U.S Championships' AND "Event" = 'All Around';