SELECT SUBSTRING_INDEX(page_title, '/', 1) AS User, COUNT(*) AS count FROM page WHERE page_namespace=2 AND page_title REGEXP '^[^/]+/Taller' GROUP BY User ORDER BY count DESC LIMIT 16;
+-----------------------+-------+
| User                  | count |
+-----------------------+-------+
| Mauriziok             |   256 |
| NataliaChile          |    92 |
| Ryoga_Nica            |    90 |
| Marisa_Glez_Glez_Glez |    72 |
| Amitie_10g            |    66 |
| Mboix                 |    61 |
| Jaluj                 |    51 |
| Porretero             |    50 |
| AnselmiJuan           |    47 |
| Giselle_Bordoy_(WMAR) |    46 |
| Linfocito_B           |    46 |
| Gmagno                |    45 |
| Cris_Evero            |    43 |
| Odalcet               |    42 |
| Verdelunar            |    41 |
| 5truenos              |    40 |
+-----------------------+-------+
16 rows in set (0.41 sec)