user: Question: Tell me the sum of year for extra of Junior team competition
Columns: ['Year', 'Tournament', 'Venue', 'Result', 'Extra']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2000.0, 'World Junior Championships', 'Santiago , Chile', '1st', '1500 m']
SQL:

assistant: SELECT SUM("Year") FROM "Table" WHERE "Extra" = 'Junior team competition';