How to Efficiently Find Overlapping Time Intervals Using SQL?

Efficiently Identifying Overlapping Time Intervals in SQL

In a scenario where you have two tables featuring start and end time fields, it becomes necessary to locate rows in the second table that intersect with the time intervals of each row in the first table. To approach this task in SQL, consider the following strategies:

SQL WHERE-Clause Approach:

For SQL Server 2005, an efficient solution can be formulated using a WHERE clause:

SELECT * 
FROM table1,table2 
WHERE table2.start <= table1.end 
AND (table2.end IS NULL OR table2.end >= table1.start)

In this query, the condition table2.start <= table1.end ensures that the start time of a row in table2 is within the interval defined by the row in table1. The condition (table2.end IS NULL OR table2.end >= table1.start) handles the case where the end time in table2 is NULL, allowing for open-ended intervals.

This approach leverages the intrinsic capabilities of SQL databases to optimize the search operation, minimizing resource consumption and query execution time.

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