带你轻松接触MySQL数据库的异常处理

标准格式

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

如果需要查看更多的错误列表可以直接到MySQL安装路径下。

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。

2、假如不需要插入ERROR CODE，可以用速记条件来代替

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、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>

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>

我们可以看到，始终执行到最后。

当然，上面的SQLSTATE '23000'可以替换为1062。

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

这个列没有默认值，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)

遇到错误时，插入的新记录。

mysql> select @x;

+------+

| @x |

+------+

| 3 |

+------+

1 row in set (0.00 sec)