SELECT COUNT(DISTINCT column(s)) FROM table
// 先group by，然后select，然后order by
select xxx from xxx where xxx and xxxx group by homework_id order by num desc limit 1;
ON DUPLICATE KEY UPDATE
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SELECT COUNT(DISTINCT column(s)) FROM table
// 先group by，然后select，然后order by
select xxx from xxx where xxx and xxxx group by homework_id order by num desc limit 1;
ON DUPLICATE KEY UPDATE
相关文章：