mysql> create table voteItem
    -> (
    ->  id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->  title varchar(30),
    ->  ticketNumber int
    -> );
Query OK, 0 rows affected (0.09 sec)

mysql>
mysql> create table ticket(
    ->  id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->  voteItemID INT references voteItem(id) ,
    ->  ip varchar(30)
    -> );
Query OK, 0 rows affected (0.09 sec)

mysql>
mysql> insert into voteItem values (null,'aaaaa',0);
Query OK, 1 row affected (0.03 sec)

mysql>
mysql> select * from voteItem;
+----+-------+--------------+
| id | title | ticketNumber |
+----+-------+--------------+
|  1 | aaaaa |            0 |
+----+-------+--------------+
1 row in set (0.00 sec)

mysql>
mysql> DELIMITER |
mysql>
mysql> CREATE TRIGGER testref AFTER INSERT ON ticket
    ->   FOR EACH ROW BEGIN
    ->          update voteItem set ticketNumber=ticketNumber+1 where id = new.v
oteItemID;
    ->   END;
    -> |
Query OK, 0 rows affected (0.09 sec)

mysql>
mysql> DELIMITER ;
mysql>
mysql> insert into ticket values (null,1,'127.0.0.1');
Query OK, 1 row affected (0.08 sec)

mysql> select * from ticket;
+----+------------+-----------+
| id | voteItemID | ip        |
+----+------------+-----------+
|  1 |          1 | 127.0.0.1 |
+----+------------+-----------+
1 row in set (0.00 sec)

mysql> select * from voteItem;
+----+-------+--------------+
| id | title | ticketNumber |
+----+-------+--------------+
|  1 | aaaaa |            1 |
+----+-------+--------------+
1 row in set (0.00 sec)

------解决方案--------------------

不建议在TRIGGER中做统计，用连接即可得到，TRIGGER少用，会影响性能