Can Merging Overlapping Date Intervals Be Optimized for Greater Efficiency?

Merge Overlapping Date Intervals

Problem:

Can the process of merging overlapping date intervals be improved?

Discussion:

The solution presented in the original post is straightforward, but there may be more efficient methods available.

Solution:

One alternative solution draws inspiration from the post "Combine overlapping datetime to return single overlapping range record."

This solution utilizes a subquery to identify the maximum end date within each interval and then performs a self-join operation to combine overlapping intervals:

SELECT 
       s1.StartDate,
       --t1.EndDate 
       MIN(t1.EndDate) AS EndDate
FROM @T s1 
INNER JOIN @T t1 ON s1.StartDate <= t1.EndDate
  AND NOT EXISTS(SELECT * FROM @T t2 
                 WHERE t1.EndDate >= t2.StartDate AND t1.EndDate < t2.EndDate) 
WHERE NOT EXISTS(SELECT * FROM @T s2 
                 WHERE s1.StartDate > s2.StartDate AND s1.StartDate <= s2.EndDate) 
GROUP BY s1.StartDate 
ORDER BY s1.StartDate 

Results:

Using this solution, the following results are obtained:

StartDate	EndDate
2010-01-01	2010-06-13
2010-06-15	2010-06-25
2010-06-26	2010-08-16
2010-11-01	2010-12-31

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