-- =============================================
-- 作    者: ruijc
-- 描    述: 将Url编码转明文字符串
-- =============================================
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

GO
SELECT dbo.FN_URLDecode(‘%E4%BD%A0%E6%98%AF%E5%93%AA%E4%B8%AA‘)

SQL 将URL编码转汉字！