How to Identify Overlapping Date Ranges in MySQL?

Identifying Overlapping Date Ranges in MySQL

Problem:

Let's consider a table that stores event sessions with their respective start and end dates. We aim to ensure that there are no conflicts between sessions. Specifically, we want to find overlapping sessions when attempting to insert a new session within a given date range.

Query:

To identify potential conflicts, we can utilize the following query:

SELECT *
FROM session
WHERE "2010-01-05" BETWEEN start_date AND end_date
   OR "2010-01-25" BETWEEN start_date AND end_date
   OR "2010-01-05" >= start_date AND "2010-01-25" <= end_date;

Understanding the Query:

This query checks for three conditions that indicate potential overlaps:

1. If the proposed start date ("2010-01-05") falls within an existing session's date range (BETWEEN start_date AND end_date).
2. If the proposed end date ("2010-01-25") falls within an existing session's date range (BETWEEN start_date AND end_date).
3. If the proposed date range (from "2010-01-05" to "2010-01-25") entirely overlaps an existing session's date range (>= start_date AND <= end_date).

Alternative Approach:

An alternative query that guarantees accurate results:

SELECT *
FROM session
WHERE new_start < existing_end
      AND new_end   > existing_start;

Explanation:

This query utilizes a logical evaluation based on four variables:

• new_start: The start date of the proposed session ("2010-01-05").
• new_end: The end date of the proposed session ("2010-01-25").
• existing_start: The start date of the existing session.
• existing_end: The end date of the existing session.

The query returns overlapping sessions if the new session's start date is before the end date of any existing session, AND the new session's end date is after the start date of any existing session.

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