mysql触发器语句

[uvcms]

写个MySql5.1.36触发器，当在AA表中列title插入数据时
判断BB表中列title是否存在相同值
如果不存在，则在BB表中列title也插入数据
如果存在，则在BB表中列num加1
怎么写阿？

[ACMAIN_CHM]

mysql> create table AA (id int primary key,title int);
Query OK, 0 rows affected (0.05 sec)

mysql> create table BB (title int primary key,num int);
Query OK, 0 rows affected (0.11 sec)

mysql> delimiter //
mysql>
mysql> create trigger tr_AA_bi before insert on AA
    -> for each row
    -> begin
    ->  insert into BB (title,num) values (new.title,1)
    ->          ON DUPLICATE KEY UPDATE num=num+1;
    -> end;
    -> //
Query OK, 0 rows affected (0.11 sec)

mysql> delimiter ;
mysql>

mysql> insert into AA values (2,1);
Query OK, 1 row affected (0.06 sec)

mysql> insert into AA values (1,1);
Query OK, 1 row affected (0.23 sec)

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

mysql> select * from bb;
+-------+------+
| title | num  |
+-------+------+
|     1 |    1 |
+-------+------+
1 row in set (0.00 sec)

mysql> select * from aa;
+----+-------+
| id | title |
+----+-------+
|  1 |     1 |
|  2 |     1 |
+----+-------+
2 rows in set (0.00 sec)

mysql> select * from bb;
+-------+------+
| title | num  |
+-------+------+
|     1 |    2 |
+-------+------+
1 row in set (0.00 sec)

mysql>

[hitexam]

create trigger testref after insert on AA
for each row
begin
set @x=(select count(*) from BB where BB.title=NEW.title);
if @x>0 then
update BB set num=num+1 where title=NEW.title;
else
insert into BB (num,title) values (1,New.title);
end if;
end;

[wfnychuan]

delimiter //
create trigger tri_update_bb after  insert on aa 
for each row 
begin 
set @n=(select count(*) from bb where bb.title=new.title); 
if @n>0 then 
update BB set num=num+1 where title=new.title; 
else 
        insert into BB(title,num) values (new.title,1); 
end if; 
end;
delimiter ;