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mysql> explain select seqnum from t7974 order by seqnum;
+----+-------------+-------+-------+---------------+---------+---------+------+-
-----+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref |
rows | Extra |
+----+-------------+-------+-------+---------------+---------+---------+------+-
-----+-------------+
| 1 | SIMPLE | t7974 | index | NULL | PRIMARY | 4 | NULL |
6111 | Using index |
+----+-------------+-------+-------+---------------+---------+---------+------+-
-----+-------------+
1 row in set (0.00 sec)