I need to run a query against a legacy table that stores URL encoded text. I need this text to be decoded in my results. How do I achieve this?
4 Answers
If you need a solution that support non english characters (unicode), there's an excelent example on CodeProject:
CREATE FUNCTION [dbo].[UrlDecode] (
@URL NVARCHAR(4000) ) RETURNS NVARCHAR(4000) AS BEGIN
DECLARE @Position INT, @Base CHAR(16), @High TINYINT, @Low TINYINT, @Pattern CHAR(21)
DECLARE @Byte1Value INT, @SurrogateHign INT, @SurrogateLow INT
SELECT @Pattern = '%[%][0-9a-f][0-9a-f]%', @Position = PATINDEX(@Pattern, @URL)
WHILE @Position > 0
BEGIN
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = 16 * @High + @Low
IF @Byte1Value < 128 --1-byte UTF-8
SELECT @URL = STUFF(@URL, @Position, 3, NCHAR(@Byte1Value)),
@Position = PATINDEX(@Pattern, @URL)
ELSE IF @Byte1Value >= 192 AND @Byte1Value < 224 AND @Position > 0 --2-byte UTF-8
BEGIN
SELECT @Byte1Value = (@Byte1Value & (POWER(2,5) - 1)) * POWER(2,6),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1)),
@URL = STUFF(@URL, @Position, 3, NCHAR(@Byte1Value)),
@Position = PATINDEX(@Pattern, @URL)
END
ELSE IF @Byte1Value >= 224 AND @Byte1Value < 240 AND @Position > 0 --3-byte UTF-8
BEGIN
SELECT @Byte1Value = (@Byte1Value & (POWER(2,4) - 1)) * POWER(2,12),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1)) * POWER(2,6),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1)),
@URL = STUFF(@URL, @Position, 3, NCHAR(@Byte1Value)),
@Position = PATINDEX(@Pattern, @URL)
END
ELSE IF @Byte1Value >= 240 AND @Position > 0 --4-byte UTF-8
BEGIN
SELECT @Byte1Value = (@Byte1Value & (POWER(2,3) - 1)) * POWER(2,18),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1)) * POWER(2,12),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1)) * POWER(2,6),
@URL = STUFF(@URL, @Position, 3, ''),
@Position = PATINDEX(@Pattern, @URL)
IF @Position > 0
BEGIN
SELECT @High = ASCII(UPPER(SUBSTRING(@URL, @Position + 1, 1))) - 48,
@Low = ASCII(UPPER(SUBSTRING(@URL, @Position + 2, 1))) - 48,
@High = @High / 17 * 10 + @High % 17,
@Low = @Low / 17 * 10 + @Low % 17,
@Byte1Value = @Byte1Value + ((16 * @High + @Low) & (POWER(2,6) - 1))
--,@URL = STUFF(@URL, @Position, 3, cast(@Byte1Value as varchar))
--,@Position = PATINDEX(@Pattern, @URL)
SELECT @SurrogateHign = ((@Byte1Value - POWER(16,4)) & (POWER(2,20) - 1)) / POWER(2,10) + 13 * POWER(16,3) + 8 * POWER(16,2),
@SurrogateLow = ((@Byte1Value - POWER(16,4)) & (POWER(2,10) - 1)) + 13 * POWER(16,3) + 12 * POWER(16,2),
@URL = STUFF(@URL, @Position, 3, NCHAR(@SurrogateHign) + NCHAR(@SurrogateLow)),
@Position = PATINDEX(@Pattern, @URL)
END
END
END
RETURN REPLACE(@URL, '+', ' ') END
I would add some additional decoding. One error I came across is the return value was null. I also noticed that a few of the answers above replaced the '+' with a space.
ALTER FUNCTION UrlDecode(@url varchar(3072))
RETURNS varchar(3072)
AS BEGIN
DECLARE @count int,
@c char(1),
@cenc char(2),
@i int,
@urlReturn varchar(3072)
SET @count = Len(@url)
SET @i = 1
SET @urlReturn = ''
WHILE (@i <= @count) BEGIN
SET @c = substring(@url, @i, 1)
IF @c LIKE '[!%]' ESCAPE '!' BEGIN
SET @cenc = substring(@url, @i + 1, 2)
SET @c = CHAR(CASE WHEN SUBSTRING(@cenc, 1, 1) LIKE '[0-9]'
THEN CAST(SUBSTRING(@cenc, 1, 1) as int)
ELSE CAST(ASCII(UPPER(SUBSTRING(@cenc, 1, 1)))-55 as int)
END * 16 +
CASE WHEN SUBSTRING(@cenc, 2, 1) LIKE '[0-9]'
THEN CAST(SUBSTRING(@cenc, 2, 1) as int)
ELSE CAST(ASCII(UPPER(SUBSTRING(@cenc, 2, 1)))-55 as int)
END)
SET @urlReturn = @urlReturn + @c
SET @i = @i + 2
END ELSE BEGIN
SET @urlReturn = @urlReturn + @c
END
SET @i = @i +1
END
IF @urlReturn is null BEGIN
set @urlReturn = ''
END ELSE BEGIN
set @urlReturn = REPLACE(@urlReturn, '+', ' ')
END
RETURN @urlReturn
END
GO
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