mysql> select a.add_date, a.seq from test as a, ( select add_date, min(seq) as mseq from test group by add_date ) b where a.add_date = b.add_date and a.seq - b.mseq < 5;

+------------+-----+

| add_date | seq |

+------------+-----+

| 2007-02-01 | 1 |

| 2007-02-02 | 2 |

| 2007-02-02 | 3 |

| 2007-02-02 | 4 |

| 2007-02-02 | 5 |

| 2007-02-02 | 6 |

| 2007-02-03 | 9 |

| 2007-02-03 | 10 |

+------------+-----+

8 rows in set (0.00 sec)

한 번 쿼리로는 잘 안되네요...