mysql> select substring_index(host,".",-1) as domain,count(*) 
       from access_log 
       group by domain 
       having domain not regexp "^[0-9]+$";

+------------+--------------+
| domain     | count(*)     |
+------------+--------------+
| au         | 2            |
| ca         | 21           |
| com        | 675          |
| de         | 40           |
| dk         | 2            |
| edu        | 1187         |
| fi         | 6            |
| fr         | 13           |
| gov        | 79           |
| hu         | 9            |
| it         | 1            |
| jp         | 1            |
| lu         | 1            |
| my         | 11           |
| net        | 308          |
| nl         | 11           |
| org        | 428          |
| ro         | 14           |
| se         | 6            |
| uk         | 246          |
+------------+--------------+
20 rows in set (0.29 sec)