sql树形结构的级联删除
root_id | son_id | uid | title | content | createdate | type | attaches |
+---------+--------+-----+--------+---------+------------+------+----------+
| 0 | 1 | 0 | 欧洲 | aaa | 1356969600 | 0 | |
| 1 | 2 | 0 | 法国 | aaa1 | 1356969600 | 0 | |
| 1 | 3 | 0 | 荷兰 | aaa2 | 1356969600 | 0 | |
| 0 | 4 | 0 | 美洲 | bbb | 1356969600 | 0 | |
| 4 | 5 | 0 | 美国 | bbb1 | 1356969600 | 0 | |
| 4 | 6 | 0 | 加拿大 | bbb2 | 1356969600 | 0 | |
| 4 | 7 | 0 | 墨西哥 | bb3 | 1356969600 | 0 | |
| 1 | 8 | 0 | 英国 | aaa3 | 1356969600 | 0 | |
| 11 | 9 | 0 | 韩国 | ccc1 | 1356969600 | 0 | |
| 11 | 10 | 0 | 中国 | ccc2 | 1356969600 | 0 | |
| 0 | 11 | 0 | 亚洲 | ccc | 1356969600 | 0 | |
| 10 | 12 | 0 | 福建省 | c2c01 | 1356969600 | 0 | |
| 10 | 13 | 0 |&nbs