SQL Server 2022

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CREATE TABLE #t
(
Code VARCHAR(MAX)
,S VARCHAR(MAX)
);

INSERT INTO #t (Code
                 ,S
                )
VALUES ('1','\String\ String'),
        ('2','Laser \Laser\'),
        ('3', 'La\ser\s and \S\trings')
SELECT *
FROM   #t;


SELECT REPLACE(REPLACE(SUBSTRING(s, start_pos,  end_pos - start_pos  
    +1), '\', '\'), '\', '\')

FROM   (SELECT s,
               CHARINDEX('\', s) AS start_pos, 
               CHARINDEX('\', s, CHARINDEX('\', s) + 1) AS end_pos
        FROM   #t) t 


Code
S


1
\String\ String

2
Laser \Laser\

3
La\ser\s and \S\trings




(No column name)


\String\

\Laser\

\ser\


SELECT
    T.Code,
    TRIM(STRING_AGG(SS.value, '') WITHIN GROUP(ORDER BY SS.ordinal)) AS Answer
FROM #t T
CROSS APPLY STRING_SPLIT(T.S, '\', 1) SS
WHERE SS.ordinal % 2 != 0 -- Keep the odd parts
GROUP BY T.Code
ORDER BY T.Code


Code
Answer


1
String

2
Laser

3
Las and trings


SELECT
    T.Code,
    CA.Answer
FROM #t T
CROSS APPLY (
    SELECT TRIM(STRING_AGG(SS.value, '') WITHIN GROUP(ORDER BY SS.ordinal)) AS Answer
    FROM STRING_SPLIT(T.S, '\', 1) SS
    WHERE SS.ordinal % 2 != 0 -- Keep the odd parts
) CA
ORDER BY T.Code


Code
Answer


1
String

2
Laser

3
Las and trings


SELECT
    T.Code,
    CA.Answer
FROM #t T
CROSS APPLY (
    SELECT TRIM(STRING_AGG(SS.value, '') WITHIN GROUP(ORDER BY SS.ordinal)) AS Answer
    FROM (
        SELECT J.value, CONVERT(int, [key]) + 1 AS ordinal
        FROM OPENJSON(CONCAT('["', REPLACE(STRING_ESCAPE(T.S, 'json'), '\\', '","'), '"]')) J
    ) SS
    WHERE SS.ordinal % 2 != 0 -- Keep the odd parts
) CA
ORDER BY T.Code


Code
Answer


1
String

2
Laser

3
Las and trings