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)
