谈谈MySQL的异常处理

shirobert

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。
标准格式
DECLARE handler_type HANDLER FOR  condition_value[,...] statement

handler_type:
  CONTINUE
| EXIT
| UNDO  --这个暂时不支持

condition_value:
SQLSTATE  [VALUE] sqlstate_value
| condition_name
|  SQLWARNING
| NOT FOUND
|  SQLEXCEPTION
| mysql_error_code
condition_value细节
1、常用MYSQL ERROR CODE 列表
http://dev.mysql.com/doc/refman/5.0/en/error-messages-server.html
更多错误列表见MySQL安装路径下
比如我的/usr/local/mysql/share/mysql/errmsg.txt
说明一下：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。
2、如果你不想插ERROR  CODE的话，
就用速记条件来代替
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、我们现在就用手册上的例子

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>  



现在来看一下遇到错误继续的情况

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();
Query OK, 0 rows affected (0.00 sec)

mysql> select @x;
+------+

| @x  |
+------+

| 3 |
+------+

1 row in set (0.00 sec)

mysql> call handlerdemo();
Query OK, 0 rows affected (0.00 sec)

mysql> select @x;
+------+

| @x  |
+------+

| 3 |
+------+

1 row in set (0.00 sec)

mysql>

可以看到，始终执行到最后。
当然，上面的SQLSTATE  '23000'可以替换为1062

我们来看一下警告。

mysql> alter table t add s2 int not null;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings:  0

此列没有默认值，插入的时候会出现警告或者1364错误提示。
mysql> DELIMITER $$
mysql> DROP PROCEDURE IF EXISTS `t_girl`.`handlerdemo`$$
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE DEFINER=`root`@`localhost` PROCEDURE `handlerdemo`()
-> BEGIN
-> DECLARE CONTINUE HANDLER FOR 1062 BEGIN END;
-> DECLARE CONTINUE HANDLER FOR SQLWARNING
-> BEGIN
-> update t set s2 = 2;
-> END;
-> DECLARE CONTINUE HANDLER FOR 1364
-> BEGIN
-> INSERT INTO t(s1,s2)  VALUES (1,3);
-> END;  
-> SET @x =  1;
-> INSERT INTO t(s1)  VALUES (1);
-> SET @x =  2;
-> INSERT INTO t(s1)  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 * from t;
+----+----+

| s1 | s2 |
+----+----+

| 1 | 3 |
+----+----+

1 row in set (0.00 sec)
遇到错误的时候插入的新记录。

mysql> select @x;
+------+

| @x  |
+------+

| 3 |
+------+

1 row in set (0.00 sec)
4、如果有新的体会，我会再发出来共享。