SQL Query to group items by time, but only if near each other?

Question

I am trying to craft a SQL statement to pull sample values from a DB. The table contains values that pertain to tool changes in a CNC machine. The current statement I have p

Answer 1

This is called the "islands problem" and I've seen this as a solution (credit Itzik Ben Gan)

select  tool_number,
        min(time) 'in',
        max(time) 'out',
        count(*)
from    (
    select  tool_number,
            time,
            ROW_NUMBER() OVER (ORDER BY time) - ROW_NUMBER() OVER (PARTITION BY Tool_Number ORDER BY time) AS Grp
    from    #temp
    ) as a
group by grp, tool_number
order by min(time)

Answer 2

Here's another approach using LAG/LEAD:

DECLARE @rawdata TABLE(Tool_Number INT, [Time] TIME(0));

INSERT @rawdata VALUES
(100,'12:00'), (100,'12:01'), (100,'12:02'), (100,'12:03'),
(200,'12:04'), (200,'12:05'),
(100,'12:06'), (100,'12:07');

;WITH x AS
(
  SELECT Tool_Number, [Time], 
    s = CASE Tool_number WHEN LAG(Tool_number,1) OVER (ORDER BY [Time]) 
        THEN 0 ELSE 1 END,
    e = CASE Tool_number WHEN LEAD(Tool_number,1) OVER (ORDER BY [Time]) 
        THEN 0 ELSE 1 END
  FROM @rawdata
),
y AS 
(
  SELECT Tool_Number, s, [Time], e = LEAD([Time],1) OVER (ORDER BY [Time]) 
  FROM x WHERE 1 IN (s,e)
)
SELECT Tool_number, TIME_IN = [Time], TIME_OUT = e 
FROM y 
WHERE s = 1
ORDER BY TIME_IN;

Results:

Tool_number  TIME_IN   TIME_OUT
-----------  --------  --------
100          12:00:00  12:03:00
200          12:04:00  12:05:00
100          12:06:00  12:07:00