SQL Server 2022

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

INSERT INTO #t (Code, S)
VALUES
    (1, '\String\ String'),
    (2, 'Laser \Laser\'),
    (3, 'La\ser\s and \S\trings'),
    (4, 'a\x\b\y\c\z'), -- missing trailing (expected result "abc")
    (5, 'a\x\\y\\\b\\\\c\\\\\z\'), -- consecutive \'s (expected result "abc")
    (6, '"a"\"x"\"b"\"y"\"c"\"z"\"d"') -- " escaped as \" when converted to JSON
SELECT *
FROM   #t;


Code
S


1
\String\ String

2
Laser \Laser\

3
La\ser\s and \S\trings

4
a\x\b\y\c\z

5
a\x\y\\b\\c\\\z\

6
"a""x""b""y""c""z""d"


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

4
abc

5
abc

6
"a""b""c""d"


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

4
abc

5
abc

6
"a""b""c""d"


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

4
abc

5
abc

6
"a""b""c""d"


-- Update in place using cross apply.
UPDATE T
SET S = 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

SELECT * FROM #t ORDER BY Code


Code
S


1
String

2
Laser

3
Las and trings

4
abc

5
abc

6
"a""b""c""d"


-- Update in place with calculation contained directly in the SET statement.
UPDATE T
SET S = (
    SELECT TRIM(STRING_AGG(SS.value, '') WITHIN GROUP(ORDER BY SS.ordinal))
    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
)
FROM #t T

SELECT * FROM #t ORDER BY Code


Code
S


1
String

2
Laser

3
Las and trings

4
abc

5
abc

6
"a""b""c""d"
Code	S
1	\String\ String
2	Laser \Laser\
3	La\ser\s and \S\trings
4	a\x\b\y\c\z
5	a\x\y\\b\\c\\\z\
6	"a""x""b""y""c""z""d"