显然这里有一个错误，但经过2个小时的尝试，我无法弄明白。也许一些新鲜的眼睛可以发现它？提前致谢！
INSERT INTO questions ( question_category, question_type, question_genre,
question_text, question_difficulty, visible, created_by, sub1, sub2, sub3)
VALUES ( {question_category}, {question_type}, {question_genre},
'{question_text}', {question_difficulty}, {visible}, '{created_by}',
{sub1}, {sub2}, {sub3})