转码前：%E5%B9%BF%E4%B8%9C%E7%9C%81%E7%8F%A0%E6%B5%B7%E5%B8%82%E4%BF%A1%E6%81%AF%E5%B7%A5%E7%A8%8B%E6%9C%89%E9%99%90%E5%85%AC%E5%8F%B8

转码后：广东省珠海市信息工程有限公司

select dbo.FN_URLDecode('%E5%B9%BF%E4%B8%9C%E7%9C%81%E7%8F%A0%E6%B5%B7%E5%B8%82%E4%BF%A1%E6%81%AF%E5%B7%A5%E7%A8%8B%E6%9C%89%E9%99%90%E5%85%AC%E5%8F%B8')

CREATE FUNCTION FN_URLDecode  
(  @Str VARCHAR(8000)--已经编码的字符串  
)  
RETURNS VARCHAR(8000)  
AS  
BEGIN  DECLARE @Position  INT;          --'%'字符所在位置  DECLARE @Chr       CHAR(16);     --字符常量  DECLARE @Pattern   CHAR(21);  DECLARE @ParseStr  VARCHAR(8000);--解码后的字符串  DECLARE @Hex       UNIQUEIDENTIFIER;--定义16进制模板,因为GUID方便转为BYTE  DECLARE @CurrWord  INT        ;--当前字  DECLARE @BitsCount INT        ;--当前解码位数  DECLARE @HightByte TINYINT;--高位字节  DECLARE @LowByte   TINYINT;--低位字节  /****************变量初始化***********************/  SET     @Chr = '0123456789abcdef';  SET     @Pattern = '%[%][a-f0-9][a-f0-9]%';  SET     @ParseStr=@Str;  SET     @Hex= '00000000-0000-0000-0000-000000000000';  SET     @CurrWord=0;  SET     @BitsCount=0;  SET     @HightByte=0;  SET     @LowByte=0;  IF (@Str IS NOT NULL OR @Str<>'')  BEGIN  SET    @Position = PATINDEX(@Pattern, @ParseStr);--取得第一个'%'所在的位置  WHILE @Position>0  BEGIN  SET @Hex=STUFF(@Hex,7,2,LEFT(RIGHT(@ParseStr,len(@ParseStr) - @Position),2));  SET @HightByte=CAST(CAST(@Hex AS BINARY(1)) AS INT);  IF (@HightByte & 127=@HightByte)  BEGIN--ASCII码直接转为UTF-8或UTF-16  SET @CurrWord=@HightByte;  SET @BitsCount=1;  END  IF (@HightByte & 192=192)  BEGIN--Unicode编码  SET @CurrWord=@HightByte & 31 ;  SET @BitsCount=2;  END  IF (@HightByte & 224=224)  BEGIN--UTF-8编码  SET @CurrWord = @HightByte & 15  SET @BitsCount = 3    END  IF (@HightByte & 240=240)  BEGIN--UTF-16编码  SET @CurrWord = @HightByte & 7  SET @BitsCount = 4    END  DECLARE @Index INT;          DECLARE @NEWCHAR NVARCHAR(2);  SET @Index=1;  SET @NEWCHAR='';  WHILE @Index<@BitsCount  BEGIN  IF (LEN(@ParseStr)-@Position-3*@Index)<0  BEGIN  SET @ParseStr=@Str ;     SET @Position=0;  BREAK;                END  SET @NEWCHAR = LEFT(RIGHT(@ParseStr,LEN(@ParseStr) - @Position - 3* @Index),2);     --如果没有16进制编码则中断外层WHILE  IF @NEWCHAR NOT LIKE '[a-f0-9][a-f0-9]'  BEGIN  SET @ParseStr = @Str  SET @Position=0;--中断外层WHILE  BREAK;  END      SET @Hex = STUFF(@Hex, 7, 2, @NEWCHAR)        SET @LowByte = CAST(CAST(@Hex AS BINARY(1)) AS INT);  IF @LowByte&192=192  BEGIN  SET @ParseStr = @Str  SET @Position=0;--中断外层WHILE  BREAK;  END   SET @CurrWord = (@CurrWord * 64) | (@LowByte & 63)                SET @Index =@Index+ 1                                                  END                                     IF @BitsCount > 1             SET @ParseStr = STUFF(@ParseStr, @Position, 3*(@BitsCount), NCHAR(@CurrWord))  ELSE   BEGIN  set @ParseStr = STUFF(@ParseStr, @Position, 2, NCHAR(@CurrWord))  set @ParseStr = STUFF(@ParseStr, @Position+1, 1, N'')         END  ----取得下一个'%'所在的位置  SET  @Position = PATINDEX(@Pattern, @ParseStr);  END  END  RETURN @ParseStr;  
END  

转自：http://blog.csdn.net/ruijc/article/details/6931189