在Doctrine中使用LIMIT的子查询

Question

我正在尝试使用Doctrine进行子查询的查询.现在它给了我一个错误.我在存储库中的功能是:

public function getRecentPlaylists($count = 3) {


    $q = $this->_em->createQuery("
            SELECT p.id,
            p.featuredImage,
            p.title,
            p.slug,         
            a.firstName,
            a.lastName,
            a.slug as authorSlug,
            (SELECT updated 
                     FROM \Entities\Articles 
                     ORDER BY updated DESC LIMIT 1) as updated
            FROM \Entities\Playlist p
            JOIN \Entities\Account a
                        ON p.account_id = a.id
            ")
        ->setMaxResults($count);

            try{    
            return $q->getResult();
            }catch(Exception $e){
                echo $e->message();
            }

}

这给了我这个错误:

[Semantical Error] line 0, col 210 near 'LIMIT 1) as updated FROM': Error: Class 'LIMIT' is not defined.

我几乎放弃了Doctrine,我无法弄清楚如何使用子查询或带有子查询的联合进行查询.有什么帮助这个功能？谢谢!

Answer 1

在这种情况下，您可以使用Doctrine的聚合表达式MAX来获取最新日期：

SELECT MAX(a.updated) FROM AppBundle:Article a

您不需要使用LIMIT。

Answer 2

你可以很容易地将自己的语法添加到Doctrine中,例如添加LIMIT 1到子查询中,正如Colin O'Dell在他的博客中所解释的那样.

// AppBundle\DBAL\FirstFunction
<?php

use Doctrine\ORM\Query\AST\Functions\FunctionNode;
use Doctrine\ORM\Query\AST\Subselect;
use Doctrine\ORM\Query\Lexer;
use Doctrine\ORM\Query\Parser;
use Doctrine\ORM\Query\SqlWalker;

/**
 * FirstFunction ::=
 *     "FIRST" "(" Subselect ")"
 */
class FirstFunction extends FunctionNode
{
    /**
     * @var Subselect
     */
    private $subselect;

    /**
     * {@inheritdoc}
     */
    public function parse(Parser $parser)
    {
        $parser->match(Lexer::T_IDENTIFIER);
        $parser->match(Lexer::T_OPEN_PARENTHESIS);
        $this->subselect = $parser->Subselect();
        $parser->match(Lexer::T_CLOSE_PARENTHESIS);
    }

    /**
     * {@inheritdoc}
     */
    public function getSql(SqlWalker $sqlWalker)
    {
        return '(' . $this->subselect->dispatch($sqlWalker) . ' LIMIT 1)';
    }
}

# app/config/config.yml
doctrine:
    # ...
    orm:
        # ...
        dql:
            string_functions:
                FIRST: AppBundle\DBAL\FirstFunction

使用方法如下:

$dqb->from('MyAppBundle:Foo', 'foo')
    ->leftJoin('foo.bar', 'bar', 'WITH', 'bar = FIRST(SELECT b FROM MyAppBundle:Bar b WHERE b.foo = foo AND b.published_date >= :now ORDER BY t.startDate)');

Answer 3

您需要的是取出内部查询并为其单独制作DQL，然后在内部使用生成的DQL

$inner_q = $this->_em
    ->createQuery("SELECT AR.updated FROM \Entities\Articles AR ORDER BY AR.updated DESC")
    ->setMaxResults(1)
    ->getDQL();

$q = $this->_em->createQuery("SELECT p.id,
        p.featuredImage,
        p.title,
        p.slug,         
        a.firstName,
        a.lastName,
        a.slug as authorSlug,
        (".$inner_q.") AS updated
        FROM \Entities\Playlist p
        JOIN \Entities\Account a
             ON p.account_id = a.id
    ")
    ->setMaxResults($count);
try{    
    return $q->getResult();
}
catch(Exception $e){
    echo $e->message();
}