FLOOR

FLOOR(X)

Devuelve el entero más grande inferior o igual a X:

mysql> SELECT FLOOR(1.23);
+-------------+
| FLOOR(1.23) |
+-------------+
|           1 |
+-------------+
1 row in set (0.00 sec)

mysql> SELECT FLOOR(-1.23);
+--------------+
| FLOOR(-1.23) |
+--------------+
|           -2 |
+--------------+
1 row in set (0.00 sec)

El valor de retorno se convierte a BIGINT.