对于MySQL的异常处理，本人不常用。不过我觉得还是有写下来的必要。
DECLARE handler_type HANDLER FOR condition_value[,...] statement
handler_type:
CONTINUE
| EXIT
| UNDO --暂时不支持
condition_value:
SQLSTATE [VALUE] sqlstate_value
| condition_name
| SQLWARNING
| NOT FOUND
| SQLEXCEPTION
| mysql_error_code
condition_value细节
1、MySQL ERROR CODE 列表
比如我的/usr/local/mysql/share/mysql/errmsg.txt
说明：SQLSTATE [VALUE] sqlstate_value这种格式是专门为ANSI SQL 和 ODBC以及其他的标准.
并不是所有的MySQL ERROR CODE 都映射到SQLSTATE。
SQLWARNING 代表所有以01开头的错误代码
NOT FOUND 代表所有以02开头的错误代码，当然也可以代表一个游标到达数据集的末尾。
SQLEXCEPTION 代表除了SQLWARNING和NOT FOUND 的所有错误代码。
3、具体示例：
CREATE TABLE t (s1 int,primary key (s1));
mysql> use t_girl
Database changed
mysql> CREATE TABLE t (s1 int,primary key (s1));
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql>
mysql> DELIMITER ||
mysql> CREATE PROCEDURE handlerdemo ()
-> BEGIN
-> DECLARE EXIT HANDLER FOR SQLSTATE '23000' BEGIN END; -- 遇到重复键值就退出
-> SET @x = 1;
-> INSERT INTO t VALUES (1);
-> SET @x = 2;
-> INSERT INTO t VALUES (1);
-> SET @x = 3;
-> END||
Query OK, 0 rows affected (0.00 sec)
mysql> DELIMITER ;
mysql> call handlerdemo();
Query OK, 0 rows affected (0.00 sec)
mysql> select @x;
+------+
| @x |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
mysql> call handlerdemo();
Query OK, 0 rows affected (0.00 sec)
mysql> select @x;
+------+
| @x |
+------+
| 1 |
+------+
1 row in set (0.00 sec)
mysql>
mysql> truncate table t;
Query OK, 0 rows affected (0.01 sec)
mysql> DELIMITER $$
mysql> DROP PROCEDURE IF EXISTS `t_girl`.`handlerdemo`$$
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE DEFINER=`root`@`localhost` PROCEDURE `handlerdemo`()
-> BEGIN
-> DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' BEGIN END;
-> SET @x = 1;
-> INSERT INTO t VALUES (1);
-> SET @x = 2;
-> INSERT INTO t VALUES (1);
-> SET @x = 3;
-> END$$
Query OK, 0 rows affected (0.01 sec)
mysql> DELIMITER ;
mysql> call handlerdemo();
0
