user: Question: Tell me the sum of Year for outcome of Runner-up for World Darts Championship
Columns: ['Outcome', 'Year', 'Championship', 'Opponent in the final', 'Score (l) = score in legs, (s) = score in sets.']
Types: ['text', 'real', 'text', 'text', 'text']
Sample row: ['Runner-up', 2010.0, 'World Darts Championship', 'Phil Taylor Category:Articles with hCards', '3–7 (s)']
SQL:

assistant: SELECT SUM("Year") FROM "Table" WHERE "Outcome" = 'Runner-up' AND "Championship" = 'World Darts Championship';