在MySQL存储过中处理SQLEXCEPTION的时候,如果你是使用GET CURRENT DIAGNOSTICS CONDITION 1 @SQL_MSG_CODE = RETURNED_SQLSTATE,@SQL_MSG_TEXT = MESSAGE_TEXT;的方式来读取那么每次显示的都是第一次报错的消息,那么如何显示当前最新的报错信息呢?请参照下例:
DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (c1 TEXT NOT NULL);
DROP PROCEDURE IF EXISTS p;
delimiter //
CREATE PROCEDURE p ()
BEGIN
-- Declare variables to hold diagnostics area information
DECLARE errcount INT;
DECLARE errno INT;
DECLARE msg TEXT;
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
-- Here the current DA is nonempty because no prior statements
-- executing within the handler have cleared it
GET CURRENT DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'current DA before mapped insert' AS op, errno, msg;
GET STACKED DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'stacked DA before mapped insert' AS op, errno, msg;
-- Map attempted NULL insert to empty string insert
INSERT INTO t1 (c1) VALUES('');
-- Here the current DA should be empty (if the INSERT succeeded),
-- so check whether there are conditions before attempting to
-- obtain condition information
GET CURRENT DIAGNOSTICS errcount = NUMBER;
IF errcount = 0
THEN
SELECT 'mapped insert succeeded, current DA is empty' AS op;
ELSE
GET CURRENT DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'current DA after mapped insert' AS op, errno, msg;
END IF ;
GET STACKED DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'stacked DA after mapped insert' AS op, errno, msg;
END;
INSERT INTO t1 (c1) VALUES('string 1');
INSERT INTO t1 (c1) VALUES(NULL);
END;
//
delimiter ;
CALL p();
SELECT * FROM t1;
需要注意的是
1.GET DIAGNOSTICS语句也会清空当前诊断区中的内容,所以上述代码中把condition handler中的insert语句去掉,得到的结果也是一样的
2.如果将上述存储过程进行如下修改,也就是将3条declare变量的语句放到
declare handler中,实际的结果将取决于MySQL的版本,如果是在MySQL-5.7.2之前的版本,下述修改后并不会影响诊断区中的内容,实际结果与上述结果相同,如果实在MySQL-5.7.2及之后的版本,declare变量语句会清空当前诊断区中的内容。
CREATE PROCEDURE p ()
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
-- Declare variables to hold diagnostics area information
DECLARE errcount INT;
DECLARE errno INT;
DECLARE msg TEXT;
GET CURRENT DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'current DA before mapped insert' AS op, errno, msg;
GET STACKED DIAGNOSTICS CONDITION 1
errno = MYSQL_ERRNO, msg = MESSAGE_TEXT;
SELECT 'stacked DA before mapped insert' AS op, errno, msg;
...
所以在需要获取诊断区中的内容时,一定要从堆栈诊断区中获取,而不是当前诊断区。