带你轻松玩转MySQL数据库的异常处理

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 --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)