How Can I Efficiently Find Overlapping Date Ranges in PostgreSQL?

Finding Overlapping Date Ranges in PostgreSQL

When working with date ranges in PostgreSQL, identifying overlaps is a crucial task. The provided query attempts to find players who were on a team during specific years but contains errors.

The Issue with the Provided Query

The query includes a BETWEEN condition (DATE_PART('YEAR',date_join) >= ? AND DATE_PART('YEAR',date_leave) <= ?), which checks if the year components of the date_join and date_leave columns are within the specified range. However, it incorrectly uses >= and <= operators, which include the upper bound (end of year).

The Corrected Query

To correctly find overlapping ranges, we need to adjust the conditions to exclude the upper bound:

SELECT * 
FROM   contract 
JOIN   team USING (name_team) 
JOIN   player USING(name_player) 
WHERE  name_team = ? 
AND    DATE_PART('YEAR',date_join) >= ? 
AND    DATE_PART('YEAR',date_leave) < ?</p>
<p><strong>Alternative Solution Using Range Types</strong></p>
<p>PostgreSQL versions 9.2 and later provide support for range types. Here's a query that utilizes a range type and the &&& operator to find overlapping ranges:</p>
<pre class="brush:php;toolbar:false">SELECT DISTINCT name_player 
FROM   contract
WHERE  name_team = ? 
AND    daterange(date_join, date_leave) &&&
       daterange '[2009-01-01,2010-01-01)'

This query leverages the overlap operator &&& and a specially defined range type to find overlapping date ranges without the need for explicit boundary checks.

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