帶你輕松玩轉MySQL數據庫的異常處理

對於MySQL的異常處理，本人不常用。不過我覺得還是有寫下來的必要。

標准格式

DECLARE handler_type HANDLER FOR condition_value[,...] statement

handler_type:

CONTINUE

| EXIT

| UNDO --暫時不支持

condition_value:

SQLSTATE [VALUE] sqlstate_value

| condition_name

| SQLWARNING

| NOT FOUND

| SQLEXCEPTION

| MySQL_error_code

condition_value細節

1、MySQL ERROR CODE 列表

如果需要查看更多的錯誤列表可以直接到MySQL安裝路徑下。

比如我的/usr/local/mysql/share/MySQL/errmsg.txt

說明：SQLSTATE [VALUE] sqlstate_value這種格式是專門為ANSI SQL 和 ODBC以及其他的標准.

並不是所有的MySQL ERROR CODE 都映射到SQLSTATE。

2、假如不需要插入ERROR CODE，可以用速記條件來代替

SQLWARNING 代表所有以01開頭的錯誤代碼

NOT FOUND 代表所有以02開頭的錯誤代碼，當然也可以代表一個游標到達數據集的末尾。

SQLEXCEPTION 代表除了SQLWARNING和NOT FOUND 的所有錯誤代碼。

3、具體示例：

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; -- 遇到重復鍵值就退出

-> 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>

遇到錯誤繼續的情況

 

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>

我們可以看到，始終執行到最後。

當然，上面的SQLSTATE '23000'可以替換為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

這個列沒有默認值，插入的時候會出現警告或者1364錯誤提示。

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)

遇到錯誤時，插入的新記錄。

MySQL> select @x;

+------+

| @x |

+------+

| 3 |

+------+

1 row in set (0.00 sec)