How to Correctly Find Overlapping Date Ranges in PostgreSQL Queries?

Finding Overlapping Date Ranges in PostgreSQL

Problem:

Your query for finding players on a team in specific years appears to be incorrect. Correct the query and provide the missing details.

Incorrect Query:

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) <= ?

Cause:

The query does not find overlapping date ranges because the BETWEEN operator is used incorrectly. The upper bound should be excluded for proper comparison.

Proper Answer:

Basic Query:

SELECT p.*
FROM team AS t
JOIN contract AS c USING (name_team)
JOIN player AS p USING (name_player)
WHERE t.name_team = ?
AND c.date_join < date '2010-01-01'
AND c.date_leave >= date '2009-01-01';

Refined Query with Distinct and NULL Handling:

SELECT DISTINCT p.*
FROM contract AS c
JOIN player AS p USING (name_player)
WHERE c.name_team = ?
AND c.date_join < date '2010-01-01'
AND (c.date_leave >= date '2009-01-01' OR c.date_leave IS NULL);

Using the OVERLAPS Operator:

SELECT DISTINCT name_player
FROM contract
WHERE name_team = ?
AND (date_join, COALESCE(date_leave, CURRENT_DATE)) OVERLAPS
(date '2009-01-01', date '2010-01-01');

Using Range Types and Index Support:

SELECT DISTINCT name_player
FROM contract
WHERE name_team = ?
AND daterange(date_join, date_leave) &&&
daterange '[2009-01-01,2010-01-01)';

Remember to replace the '?' placeholders with the necessary values in your queries.

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