In the sixth round, what is the sum of fixtures when there were more than 15 clubs involved?
CREATE TABLE table_name_67 (
    fixtures INTEGER,
    round VARCHAR,
    clubs_involved VARCHAR
)
SELECT SUM(fixtures) FROM table_name_67 WHERE round = "sixth round" AND clubs_involved > 15
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: In the sixth round, what is the sum of fixtures when there were more than 15 clubs involved? ### Input: CREATE TABLE table_name_67 (
    fixtures INTEGER,
    round VARCHAR,
    clubs_involved VARCHAR
) ### Response: SELECT SUM(fixtures) FROM table_name_67 WHERE round = "sixth round" AND clubs_involved > 15