Find first character position that is different between two strings [closed] - sql-server-2008

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In this Question the accepted solution using bitwise XOR in PHP to find first different Charindex of two string. How can implement this solution in SQL query or is there a better solution for this problem?

Answer 1

Update: Here's Sql XOR solution:
only for string with len letter than 8
DECLARE #A VARCHAR(50)
DECLARE #B VARCHAR(50)
DECLARE #Pos INT
set #A='ABrC12#4'
set #B='ABrC1234'
SET #Pos=( select
case
when len(#A)<>LEN(#B) then -1
when #A=#B then 0
ELSE 1+PATINDEX('%[1-9]%',
CONVERT(varchar(max),cast(cast(CAST(#A AS varbinary) as BIGINT) ^
cast(CAST(#B AS varbinary) as BIGINT)
as varbinary ),2))/2
end)
Print #Pos
You can use a little nice result with this:
create FUNCTION [dbo].[fnFirstPosDif]
(
#Word as Nvarchar(70),
#Word2 as Nvarchar(70)
)
RETURNS INT
AS
BEGIN
declare #Strings2 TABLE
(
FirstPosDif INT
)
declare #FirstPosDif as int
;with C as
(
select #Word as Word,#Word2 as Word2 ,0 as Iteration
union all
select cast(substring(#Word,Iteration+1,1)as Nvarchar(70)) as Word,cast(substring(#Word2,Iteration+1,1)as Nvarchar(70)) as Word2,Iteration + 1 from C
WHERE Iteration < len(#Word) and cast(substring(#Word,Iteration+1,1)as Nvarchar(70))=cast(substring(#Word2,Iteration+1,1)as Nvarchar(70))
)
insert into #Strings2(FirstPosDif) select MAX(Iteration) as FirstPosDif from C
set #FirstPosDif=(select top 1 FirstPosDif from #Strings2)
return #FirstPosDif
END

Answer 2

I do not believe that there is an equivalent to any of the methods shown in the question you referenced for SQL Server.
The only way appears to be to manually walk through the string (as per the PHP suggestion), but in SQL it is even more laborious due to the fact that you cannot address CHAR types as if they were arrays:
DECLARE #A NVARCHAR(50)
DECLARE #B NVARCHAR(50)
DECLARE #I INT
DECLARE #Pos INT
SET #A = 'Hello World!'
SET #B = 'Hella World!'
SET #I = 0
SET #Pos = 0
-- Loop through each character
WHILE (#I < LEN(#A) AND #I < LEN(#B) AND #Pos = 0)
BEGIN
-- See if the characters at this position differ
IF (SUBSTRING(#A, #I, 1) != SUBSTRING(#B, #I, 1))
SET #Pos = #I
SET #I = #I + 1
END
IF (#Pos > 0)
PRINT 'Difference at position ' + CAST(#Pos AS VARCHAR) + ' A:' + SUBSTRING(#A, #Pos, 1) + ' B:' + SUBSTRING(#B, #Pos, 1)
ELSE
PRINT 'Strings are the same'
Running this as per the above would yield the following output:
Difference at position 5 A:o B:a
Note that you could put this into a UDF for simplicity if you use it often, and additionally I have not included checks for NULL values.