如何删除重复的行并保留第一行？

MySQL在DELETe语句中支持JOIN。如果要保留第一个重复项：

DELETE a  FROM MYVIEWS a  JOIN (SELECt MIN(t.a1) AS min_a1, t.k1, t.k2, t.k3          FROM MYVIEWS t      GROUP BY t.k1, t.k2, t.k3        HAVINg COUNT(*) > 1) b ON b.k1 = a.k1        AND b.k2 = a.k2        AND b.k3 = a.k3        AND b.min_a1 != a.a1

如果要保留最后一个重复项：

DELETe a  FROM MYVIEWS a  JOIN (SELECt MAX(t.a1) AS max_a1, t.k1, t.k2, t.k3          FROM MYVIEWS t      GROUP BY t.k1, t.k2, t.k3        HAVINg COUNT(*) > 1) b ON b.k1 = a.k1        AND b.k2 = a.k2        AND b.k3 = a.k3        AND b.max_a1 != a.a1