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DECLARE @Str1 VARCHAR(45) = 'Interesting',
@Str2 VARCHAR(45) = 'Interested';
WITH CTE AS
(
SELECT 1 Num
UNION ALL
SELECT Num + 1
FROM CTE
WHERE Num < (SELECT CASE WHEN LEN(@Str1) > LEN(@Str2) THEN
LEN(@Str1)
ELSE LEN(@Str2)
END)
)
,
F AS
(
SELECT *, @Str1 Str1, @Str2 Str2,
CASE WHEN SUBSTRING(@Str1, Num, 1) = SUBSTRING(@Str2, Num, 1) THEN 0
ELSE 1
END IsTheSame
FROM CTE
)
SELECT TOP 1 Num
FROM F
WHERE IsTheSame = 1
ORDER BY Num ASC;
