Как в MSSQL разделить таблицу на отрезки времени по значению?

Один из вариантов решения - рекурсивная проверка на совпадение dt_end с dt_begin при изменении значения val:

-- входные данные
WITH [tempTable] AS (
  SELECT CONVERT([datetime], '2023-04-11 13:35:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:36:00.000', 120) AS [dt_end], CAST(0 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:36:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:37:00.000', 120) AS [dt_end], CAST(0 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:37:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:38:00.000', 120) AS [dt_end], CAST(1 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:38:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:39:00.000', 120) AS [dt_end], CAST(1 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:39:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:40:00.000', 120) AS [dt_end], CAST(1 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:40:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:41:00.000', 120) AS [dt_end], CAST(0 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:41:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:42:00.000', 120) AS [dt_end], CAST(0 AS [int]) AS [val]
  UNION ALL
  SELECT CONVERT([datetime], '2023-04-11 13:42:00.000', 120) AS [dt_beg], CONVERT([datetime], '2023-04-11 13:43:00.000', 120) AS [dt_end], CAST(0 AS [int]) AS [val]
),

[recursive] AS (
  -- фиксируем изменение val
  SELECT 
    t1.[dt_beg],
    t1.[dt_end],
    t1.[val]
  FROM
    [tempTable] t1
  WHERE
    NOT EXISTS (
      SELECT 1
      FROM [tempTable] t2
      WHERE
        t2.[dt_end] = t1.[dt_beg]
        AND t2.[val] = t1.[val]
    )
  UNION ALL
  -- рекурсивная выборка
  SELECT
    r.[dt_beg],
    t.[dt_end],
    r.[val]
  FROM 
    [recursive] r
    INNER JOIN [tempTable] t ON t.[dt_beg] = r.[dt_end] AND r.[val] = t.[val]
)

-- финальная группировка
SELECT
  r.[dt_beg],
  MAX(r.[dt_end]) AS [dt_end],
  r.[val]
FROM
  [recursive] r
GROUP BY
  r.[dt_beg],
  r.[val]
ORDER BY
  r.[dt_beg]