user: Question: what is the venue when the result is 2nd and extra is 4 x 100 m relay?
Columns: ['Year', 'Tournament', 'Venue', 'Result', 'Extra']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1971.0, 'European Indoor Championships', 'Sofia , Bulgaria', '2nd', '4 x 200 m relay']
SQL:

assistant: SELECT "Venue" FROM "Table" WHERE "Result" = '2nd' AND "Extra" = '4 x 100 m relay';