Olá Daniel,
Você pode usar a função floor que não lhe trará problemas com arredondamento -
http://dev.mysql.com/doc/refman/5.6/en/mathematical-functions.html#function_floor
mysql> CREATE table teste (valor DOUBLE);
Query OK, 0 rows affected (0.06 sec)
mysql> INSERT INTO teste VALUES (10.8888), (11.2548), (100.2348);
Query OK, 3 rows affected (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM teste;
+----------+
| valor |
+----------+
| 10.8888 |
| 11.2548 |
| 100.2348 |
+----------+
3 rows in set (0.00 sec)
mysql> UPDATE teste SET valor = FLOOR(valor);
Query OK, 3 rows affected (0.01 sec)
Rows matched: 3 Changed: 3 Warnings: 0
mysql> SELECT * FROM teste;
+-------+
| valor |
+-------+
| 10 |
| 11 |
| 100 |
+-------+
3 rows in set (0.00 sec)
Ou você pode usar a função CAST, CONVERT que irá arredondar os valores -
https://dev.mysql.com/doc/refman/5.6/en/cast-functions.html
mysql> TRUNCATE teste;
Query OK, 0 rows affected (0.05 sec)
mysql> INSERT INTO teste VALUES (10.8888), (11.2548), (100.2348);
Query OK, 3 rows affected (0.01 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM teste;
+----------+
| valor |
+----------+
| 10.8888 |
| 11.2548 |
| 100.2348 |
+----------+
3 rows in set (0.00 sec)
mysql> UPDATE teste SET valor = CAST(valor as SIGNED);
Query OK, 3 rows affected (0.01 sec)
Rows matched: 3 Changed: 3 Warnings: 0
mysql> SELECT * FROM teste;
+-------+
| valor |
+-------+
| 11 |
| 11 |
| 100 |
+-------+
3 rows in set (0.00 sec)
mysql> TRUNCATE teste;
Query OK, 0 rows affected (0.03 sec)
mysql> INSERT INTO teste VALUES (10.8888), (11.2548), (100.2348);
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> UPDATE teste SET valor = CONVERT(valor, SIGNED);
Query OK, 3 rows affected (0.01 sec)
Rows matched: 3 Changed: 3 Warnings: 0
mysql> SELECT * FROM teste;
+-------+
| valor |
+-------+
| 11 |
| 11 |
| 100 |
+-------+
3 rows in set (0.00 sec)