DQL Select every rows having one column's MAX value

Question

Working with Symfony 2 and Doctrine, I\'m searching for a way to select every rows having the max value in a specific column.

Right now, I\'m doing it in two queries

Answer 1

For me when i trying to make a subquery i make:

->andWhere($qb->expr()->eq('affaire', $qb2->getDql()));

Answer 2

After some hours of headache and googling and stackOverflow readings... I finally found out how to make it.

Here is my final DQL queryBuilder code:

    $qb = $this->createQueryBuilder('a');
    $qb2= $this->createQueryBuilder('mss')
            ->select('MAX(mss.periodeComptable) maxPeriode')
            ->where('mss.affaire = a')
            ;

    $qb ->innerJoin('GAAffairesBundle:MontantMarche', 'm', 'WITH', $qb->expr()->eq( 'm.periodeComptable', '('.$qb2->getDQL().')' ))
        ->where('a = :affaire')
        ->setParameter('affaire', $affaire)
        ;

    return $qb->getQuery()->getResult();

Answer 3

To achieve this using pure DQL and without use of any aggregate function you can write doctrine query as

SELECT a
FROM GAAffairesBundle:MontantMarche a
    LEFT JOIN GAAffairesBundle:MontantMarche b
    WITH a.affaire = b.affaire 
    AND a.periodeComptable < b.periodeComptable
WHERE b.affaire IS NULL
ORDER BY a.periodeComptable DESC

The above will return you max record per group (per affaire)

Expalnation

The equivalent SQL for above DQL will be like

SELECT a.*
FROM MontantMarche a
LEFT JOIN MontantMarche b 
    ON a.affaire = b.affaire 
    AND a.periodeComptable < b.periodeComptable
WHERE b.affaire IS NULL
ORDER BY a.periodeComptable DESC

Here i assume there can be multiple entries in table e.g(MontantMarche) for each affaire, so here i am trying to do a self join on affaire and another tweak in join is i am trying to join only rows from right table(b) where a's periodeComptable < b's periodeComptable, So the row for left table (a) with highest periodeComptable will have a null row from right table(b) thus to pick the highest row per affaire the WHERE right table row IS NULL necessary.

Similarly using your posted sample query with inner join can be written as

select yt.id, yt.rev, yt.contents
from YourTable yt
left join YourTable ss on yt.id = ss.id and yt.rev < ss.rev
where ss.rev is null

Hope it makes sense