mysql> create table t1(id int, val int);
Query OK, 0 rows affected (0.49 sec)

mysql> create table t2(id int, val int);
Query OK, 0 rows affected (0.22 sec)

mysql> create function genval(i int) returns int not deterministic return 10*rand() + i;
Query OK, 0 rows affected (0.24 sec)

mysql> delimiter @@
mysql> create trigger tt1 before insert on t1
    -> for each row begin
    -> set new.val = genval(new.id);
    -> end;
    -> @@
Query OK, 0 rows affected (0.07 sec)

mysql> create trigger tt2 before insert on t2
    -> for each row begin
    -> set new.val = genval(new.id);
    -> end;
    -> @@
Query OK, 0 rows affected (0.04 sec)

mysql> delimiter ;
mysql> insert into t1(id) values (11),(22);
Query OK, 2 rows affected (0.08 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> insert into t2(id) select 33 union select 44;
Query OK, 2 rows affected (0.04 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from t1;
+------+------+
| id   | val  |
+------+------+
|   11 |   13 |
|   22 |   31 |
+------+------+
2 rows in set (0.03 sec)

mysql> select * from t2;
+------+------+
| id   | val  |
+------+------+
|   33 |   42 |
|   44 |   52 |
+------+------+
2 rows in set (0.00 sec)

mysql>