SQL - Replace characters using mapping, without a loop - sql

Question

Is there a way to replace characters in SQL Server from a string using a mapping table and without using a loop.
I have mapping that can go like this:
a => b
b => c
...
z => a
This mapping is not static and can change.
I tried the solution from https://stackoverflow.com/a/45202933/3161817 and https://stackoverflow.com/a/13051989/3161817 but I only end up having a string that are just a, like 'aaaaaaaa'
My current solution is like:
DECLARE #NextChar NCHAR(1)
DECLARE #Position int = 1
DECLARE #StrLength int = LEN(#str)
DECLARE #Result nvarchar(1000) = ''
WHILE (#Position <= #StrLength)
BEGIN
SET #NextChar = SUBSTRING(#str, #Position, 1)
SET #Result = #Result + ISNULL((SELECT ToChar FROM CharMapping
WHERE #NextChar COLLATE Latin1_General_BIN = FromChar COLLATE Latin1_General_BIN
), #NextChar)
SET #Position= #Position + 1
END
but I'm looking for a possible solution without a loop.

Answer 1

DECLARE #t TABLE(
src char
,dest char
)
INSERT INTO #t VALUES
('a', 'b')
,('b', 'c')
,('d', 'e')
DECLARE #TestString nvarchar(100) = 'aabbcdacbezzz';
WITH cte AS(
SELECT 1 lvl, SUBSTRING(#TestString, 1, 1) AS TestPosChar, SUBSTRING(#TestString, 2, LEN(#TestString)-1) AS TestStringRemain
UNION ALL
SELECT lvl + 1, SUBSTRING(TestStringRemain, 1, 1), SUBSTRING(TestStringRemain, 2, LEN(TestStringRemain)-1)
FROM cte
WHERE LEN(TestStringRemain) >= 1
)
SELECT #TestString AS OldString
,SUBSTRING((SELECT ( '' + ISNULL(t.dest, TestPosChar))
FROM cte c
LEFT JOIN #t AS t ON t.src = c.TestPosChar
ORDER BY lvl
FOR XML PATH( '' )
), 1, 1000 ) AS NewString

Answer 2

I made this test :
declare #MyTab table(
letter char
)
declare #MyTab2 table(
letter char
)
insert into #MyTab
select substring(a.b, v.number+1, 1)
from (select 'ABCDEFGHZZZ' b) a
join master..spt_values v on v.number < len(a.b)
where v.type = 'P'
insert into #MyTab2
select NewLetter
from (
select case letter when 'Z' then 'A'
when 'z' then 'a'
else char(ascii(letter)+1) end NewLetter
from #MyTab
) MyView
select stuff(
(select ''+letter from #MyTab2
for xml path('')),1,0,'')

Answer 3

SQL Server 2017 introduces a TRANSLATE function, which is similar to nested REPLACE functions. You didn't specify what version of SQL Server you are using so I don't know if that's an option.
SELECT TRANSLATE(#SourceString, 'abcdefghijklmnopqrstuvwxyz', 'bcdefghijklmnopqrstuvwxyza');

Answer 4

Try (and expand) following query, which use XML PATH, a tally number table and a decode table:
CREATE TABLE #TTMMPP (ORIG CHAR(1), NEWC CHAR(1));
/* add all values to shift */
INSERT INTO #TTMMPP VALUES ('a','b'),('b','c'),('c','d'),('d','e'),('e','f') /*, ....*/
;
/* N as max len of your string */
CREATE TABLE #TTMMPP2 (N smallint);
DECLARE #I INT
DECLARE #ROWS INT
SET #I = 1
SET #ROWS = 1000
WHILE #I < #ROWS
BEGIN
INSERT INTO #TTMMPP2 VALUES (#I)
SET #I = #I + 1
END
----------------------------------------
DECLARE #my_str VARCHAR(100) = 'abcd';
SELECT #my_str AS ORIGINAL,
(
SELECT ''+C.NEWC
FROM (
SELECT N, SUBSTRING( #my_str, N,1) AS X, B.NEWC
FROM #TTMMPP2 A
INNER JOIN #TTMMPP B ON SUBSTRING(#my_str,A.N,1)= B.ORIG
WHERE N<=LEN(#my_str)
) C
FOR XML PATH('')
) AS SHIFTED;
Output:
ORIGINAL SHIFTED
abcd bcde
Updated version: if you want "mark" character not found in decode table you can use this (little changes to query: LEFT JOIN and COALESCE):
DECLARE #my_str VARCHAR(100) = 'abcdefg';
SELECT #my_str AS ORIGINAL,
(
SELECT ''+C.NEWC
FROM (
SELECT N, SUBSTRING( #my_str, N,1) AS X, COALESCE(B.NEWC,'*') AS NEWC
FROM #TTMMPP2 A
LEFT JOIN #TTMMPP B ON SUBSTRING(#my_str,A.N,1)= B.ORIG
WHERE N<=LEN(#my_str)
) C
ORDER BY N
FOR XML PATH('')
) AS SHIFTED;
Output (* substitute character not found in decode table):
ORIGINAL SHIFTED
abcdefg bcde***
New update (as your last comment added):
SELECT #my_str AS ORIGINAL,
(
SELECT ''+C.NEWC
FROM (
SELECT N, SUBSTRING( #my_str, N,1) AS X, COALESCE(B.NEWC,SUBSTRING(#my_str,A.N,1)) AS NEWC
FROM ##TTMMPP2 A
LEFT JOIN #TTMMPP B ON SUBSTRING(#my_str,A.N,1) COLLATE Latin1_General_BIN = B.ORIG COLLATE Latin1_General_BIN
WHERE N<=LEN(#my_str)
) C
ORDER BY N
FOR XML PATH('')
) AS SHIFTED
Output:
ORIGINAL SHIFTED
abcdefgA bcdeefgA