How Can We Efficiently Identify Overlapping Date Ranges in SQL?

SQL date range comparison

When working with date ranges stored in the database, it may be necessary to determine whether a specific date range overlaps any existing ranges. This is a recurring problem in SQL databases.

One way to solve this problem is to invert the comparison logic. Instead of finding ranges that overlap with a given range, we're looking for ranges that don't overlap. By identifying periods that do not overlap, we can conclude that the remaining periods are those that do overlap.

To illustrate this logic, let us examine the following example:

<code>           |-------------------|          与之比较
               |---------|                包含在内
           |----------|                   包含在内，起始时间相同
                   |-----------|          包含在内，结束时间相同
           |-------------------|          包含在内，起始和结束时间相同
     |------------|                       未完全包含，起始时间重叠
                   |---------------|      未完全包含，结束时间重叠
     |-------------------------|          起始时间重叠，范围更大
           |-----------------------|      结束时间重叠，范围更大
     |------------------------------|     完全重叠</code>

As can be seen from the figure, periods that do not overlap with the comparison period either start after the comparison period ends or end before the comparison period starts.

In contrast, periods that overlap with the comparison period fall into the following categories:

• Included within comparison period
• Contained within the comparison period, with the same start or end time
• Overlaps with the start or end time of the comparison period
• Completely overlapping comparison periods

Translating this logic into SQL, we can use the following query to retrieve all epochs that overlap with a given check epoch:

<code class="language-sql">SELECT *
FROM periods
WHERE range_start < @check_period_end AND range_end > @check_period_start;</code>

By reversing the logic to find non-overlapping epochs, we can effectively identify and exclude these epochs from the results, leaving a list of matching epochs.

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