How to Ensure Non-Overlapping Date Ranges in MySQL\'s `avail` Table?

MySQL: Inserting Date Range into Date Columns Only if No Overlap Exists

Problem Statement

Given a table named avail that stores date ranges of availability for different acc_ids, the objective is to validate and insert new date ranges without overlapping existing ones for the same acc_id. Specifically, any kind of overlap must be avoided, including start and end dates that match existing ones.

Proposed Solution

One-Statement Approach:

Regrettably, it is not possible to implement this validation using a single insert statement in MySQL due to the lack of SQL CHECK constraints.

Alternative Approaches:

SQL Trigger:

An SQL trigger can be used to enforce this constraint before the insert or update operation is performed. The trigger would check for overlapping rows and throw an error using the SIGNAL statement. However, this approach requires using an up-to-date version of MySQL.

Application Logic:

The most practical approach is to perform the validation within the application logic. A SELECT COUNT(id) statement can be used to retrieve the number of rows that would be violated by the new range. If the count is greater than 0, the insert/update operation should be aborted.

Checking for Insert Failure:

Rows affected can be checked to determine if the insert was successful or failed. A value of 0 indicates a failure, which could be due to date overlap or other reasons.

Example:

<code class="sql">SELECT COUNT(id)
FROM avail
WHERE
  acc_id = <new_acc_id>
  AND (
    (start_date <= <new_start_date> AND end_date >= <new_start_date>)
    OR (start_date <= <new_end_date> AND end_date >= <new_end_date>)
  );</code>

If the returned count is greater than 0, the insert operation should not be performed.

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