How Can I Efficiently Compare Date Ranges in MySQL?

Efficiently Comparing Date Ranges in MySQL

This guide demonstrates how to efficiently compare date ranges in MySQL, focusing on determining overlaps between a target range and a set of predefined ranges.

A Simplified Approach

Instead of directly comparing ranges for overlap, a more efficient method involves checking for non-overlap. This simplifies the logical process.

Understanding Overlapping Ranges

An overlap occurs when a predefined range meets one of these conditions relative to the target range:

• Complete Containment: The predefined range falls entirely within the target range.
• Partial Overlap: The predefined range overlaps at either its start or end point.
• Complete Overlap: The predefined range completely encompasses the target range.

Identifying Non-Overlapping Ranges

Conversely, non-overlapping ranges satisfy these conditions:

• Precedes Target: The predefined range ends before the target range begins.
• Follows Target: The predefined range starts after the target range ends.

SQL Query for Overlapping Ranges

To identify all rows in the periods table (with range_start and range_end columns) that overlap with a target range (@check_period_start, @check_period_end):

<code class="language-sql">SELECT *
FROM periods
WHERE NOT (range_start > @check_period_end OR range_end < @check_period_start);</code>

The NOT operator inverts the condition, effectively selecting only the rows where an overlap exists.

Alternative Query: Direct Overlap Check

Alternatively, to directly select overlapping rows:

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

This query directly checks if the predefined range start is before or equal to the target range end, and if the predefined range end is after or equal to the target range start. This approach might be slightly more readable for some.

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