INT8 is a synonym for BIGINT.

CREATE TABLE t1 (x INT8);

DESC t1;
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| x     | bigint(20) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+