[mysql] 二進制數據編輯方法

需求：按C++格式保存如下結構到mysql blob 字段

typedef struct _MailSubAttachHead
{
	BYTE byType;
	BYTE byIdx;
	WORD wDataLen;
	INT iData1;
	INT iData2;
}TMailSubAttachHead;

MYSQL 中的存儲過程處理（注意變量定義要指定爲CHARACTER SET 'latin1'，否則會出現錯誤：DB默認是utf8）
ERROR 1366 (HY000): Incorrect string value: '\xE8\x03\x00\x00' for column '__AttachContent' at row 1

DROP FUNCTION IF EXISTS clr_int2byte;
DELIMITER $$

create function clr_int2byte(_data int unsigned )
returns binary(4)
begin
  return concat(char(_data    & 0x000000FF),
				char(_data>>8 & 0x000000FF),
				char(_data>>16& 0x000000FF),
				char(_data>>24& 0x000000FF));
end$$
DELIMITER ;

DROP FUNCTION IF EXISTS clr_word2byte;
DELIMITER $$

create function clr_word2byte(_data SMALLINT unsigned )
returns binary(2)
begin
  return concat(char(_data    & 0x00FF),
				char(_data>>8 & 0x00FF));
end$$

DELIMITER ;

DROP PROCEDURE IF EXISTS Prws_Game_CreateMail;
DELIMITER $$

CREATE  DEFINER=`root`@`%` PROCEDURE test()
BEGIN
	DECLARE __AttachContent VARCHAR(2048)  CHARACTER SET 'latin1' DEFAULT '';
	--                                            byType  byIdx   wDataLen          iData1              iData2
	SET __AttachContent = CONCAT(__AttachContent, CHAR(1),CHAR(0),clr_word2byte(8), clr_int2byte(100) , clr_int2byte(200) );
	SET __AttachContent = CONCAT(__AttachContent, CHAR(1),CHAR(1),clr_word2byte(8), clr_int2byte(1100), clr_int2byte(2200));
END;
$$
DELIMITER ;
call Prws_test (1000);