Question

我有两个查询需要尝试合并，以便我的分页正常工作，并且帖子以正确的顺序显示。

我有一个问题：

$today = date('m/d/Y', strtotime('today'));

$args = array(
    'post_type' => 'workshops',
    "posts_per_page" => 5,
    "paged" => $paged,
    'meta_key' => 'select_dates_0_workshop_date',
    'orderby' => 'meta_value',
    'order' => 'ASC',
        'meta_query' => array(
            array(
                  'key' => 'select_dates_0_workshop_date',
                  'meta-value' => "meta_value",
                  'value' => $today,
                  'compare' => '>=',
                  'type' => 'CHAR'
             )
    )
    );

此查询的结果需要在上面的查询之后：

$args = array(
    'post_type' => 'workshops',
    "posts_per_page" => 5,
    "paged" => $paged,
    'meta_key' => 'select_dates_0_workshop_date',
    'orderby' => 'meta_value',
    'order' => 'DESC',
        'meta_query' => array(
            array(
                 'key' => 'select_dates_0_workshop_date',
                 'meta-value' => "meta_value",
                 'value' => $today,
                 'compare' => '<',
                 'type' => 'CHAR'
        )
    )
    );

两个查询之间的差异是：'order'和'compare'。

我在纯MYSQL查询中完成了这个，但我不确定如何在WordPress上执行此操作

Answer 1

这是答案的更新版本，比上一个版本更灵活。

以下是使用SQL UNION：

的一个想法

我们可以使用posts_clauses过滤器中的数据来重写posts_request过滤器中的SQL查询。
我们扩展WP_Query课程以实现我们的目标。我们实际上做了两次：
- WP_Query_Empty：获取每个子查询生成的SQL查询，但不进行数据库查询。
- WP_Query_Combine：获取帖子。
以下实现支持组合N子查询。

以下是两个演示：

演示＃1：

假设您有六个帖子，按日期排序（DESC）：

CCC
AAA
BBB
CCC
YYY
ZZZ
XXX

XXX，YYY和ZZZ的日期早于DT=2013-12-14 13:03:40。

让我们对我们的帖子进行排序，以便DT之后发布的帖子按标题排序（ASC），并在DT按标题排序之前发布publisehd（DESC）：

AAA
BBB
CCC
ZZZ
YYY
XXX

然后我们可以使用以下内容：

/**
 * Demo #1 - Combine two sub queries:
 */

$args1 = array(
    'post_type'  => 'post',
    'orderby'    => 'title',
    'order'      => 'ASC',
    'date_query' => array(
        array( 'after' => '2013-12-14 13:03:40' ),
    ),
);

$args2 = array(
    'post_type'  => 'post',
    'orderby'    => 'title',
    'order'      => 'DESC',
    'date_query' => array(
        array( 'before' => '2013-12-14 13:03:40', 'inclusive' => TRUE ),    
    ),
);

$args = array( 
   'posts_per_page' => 1,
   'paged'          => 1,
   'sublimit'       => 1000,
   'args'           => array( $args1, $args2 ),
);

$results = new WP_Combine_Queries( $args );

这将生成以下SQL查询：

SELECT SQL_CALC_FOUND_ROWS * FROM ( 
    ( SELECT wp_posts.* 
        FROM wp_posts 
        WHERE 1=1 
            AND ( ( post_date > '2013-12-14 13:03:40' ) ) 
            AND wp_posts.post_type = 'post' 
            AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') 
            ORDER BY wp_posts.post_title ASC 
            LIMIT 1000
    ) 
    UNION 
    ( SELECT wp_posts.* 
        FROM wp_posts 
        WHERE 1=1 
        AND ( ( post_date <= '2013-12-14 13:03:40' ) ) 
        AND wp_posts.post_type = 'post' 
        AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') 
        ORDER BY wp_posts.post_title DESC 
        LIMIT 1000
    ) 
) as combined LIMIT 0, 10

演示＃2：

以下是您的例子：

/**
 * Demo #2 - Combine two sub queries:
 */

$today = date( 'm/d/Y', strtotime( 'today' ) );

$args1 = array(
    'post_type'      => 'workshops',
    'meta_key'       => 'select_dates_0_workshop_date',
    'orderby'        => 'meta_value',
    'order'          => 'ASC',
    'meta_query'     => array(
        array(
            'key'         => 'select_dates_0_workshop_date',
            'value'       => $today,
            'compare'     => '>=',
            'type'        => 'CHAR',
        ),
    )
);

$args2 = array(
    'post_type'      => 'workshops',
    'meta_key'       => 'select_dates_0_workshop_date',
    'orderby'        => 'meta_value',
    'order'          => 'DESC',
    'meta_query'     => array(
        array(
            'key'         => 'select_dates_0_workshop_date',
            'value'       => $today,
            'compare'     => '<',
            'type'        => 'CHAR',
        ),
    )
);

$args = array( 
   'posts_per_page' => 5,
   'paged'          => 4,
   'sublimit'       => 1000,
   'args'           => array( $args1, $args2 ),
);

$results = new WP_Combine_Queries( $args );

这应该给你一个像这样的查询：

SELECT SQL_CALC_FOUND_ROWS * FROM ( 
    ( SELECT wp_posts.* 
        FROM wp_posts 
        INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) 
        INNER JOIN wp_postmeta AS mt1 ON (wp_posts.ID = mt1.post_id) 
        WHERE 1=1 
            AND wp_posts.post_type = 'workshops' 
            AND (wp_posts.post_status = 'publish' OR wp_posts.post_author = 1 AND wp_posts.post_status = 'private') 
            AND (wp_postmeta.meta_key = 'select_dates_0_workshop_date' AND (mt1.meta_key = 'select_dates_0_workshop_date' AND CAST(mt1.meta_value AS CHAR) >= '05/16/2014') ) 
            GROUP BY wp_posts.ID 
            ORDER BY wp_postmeta.meta_value ASC
            LIMIT 1000 
        ) 
    UNION 
    ( SELECT wp_posts.* 
        FROM wp_posts 
        INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) 
        INNER JOIN wp_postmeta AS mt1 ON (wp_posts.ID = mt1.post_id) 
        WHERE 1=1 
            AND wp_posts.post_type = 'workshops' 
            AND (wp_posts.post_status = 'publish' OR wp_posts.post_author = 1 AND wp_posts.post_status = 'private') 
            AND (wp_postmeta.meta_key = 'select_dates_0_workshop_date' AND (mt1.meta_key = 'select_dates_0_workshop_date' AND CAST(mt1.meta_value AS CHAR) < '05/16/2014') ) 
            GROUP BY wp_posts.ID 
            ORDER BY wp_postmeta.meta_value DESC 
            LIMIT 1000 
        ) 
) as combined LIMIT 15, 5

演示＃3：

我们还可以组合两个以上的子查询：

/**
 * Demo #3 - Combine four sub queries:
 */

$args = array( 
   'posts_per_page' => 10,
   'paged'          => 1,
   'sublimit'       => 1000,
   'args'           => array( $args1, $args2, $args3, $args4 ),
);

$results = new WP_Combine_Queries( $args );

类：

以下是我们的演示类：

/**
 * Class WP_Combine_Queries
 * 
 * @uses WP_Query_Empty
 * @link https://stackoverflow.com/a/23704088/2078474
 *
 */

class WP_Combine_Queries extends WP_Query 
{
    protected $args    = array();
    protected $sub_sql = array();
    protected $sql     = '';

    public function __construct( $args = array() )
    {
        $defaults = array(
            'sublimit'       => 1000,
            'posts_per_page' => 10,
            'paged'          => 1,
            'args'           => array(),
        );

        $this->args = wp_parse_args( $args, $defaults );

        add_filter( 'posts_request',  array( $this, 'posts_request' ), PHP_INT_MAX  );

        parent::__construct( array( 'post_type' => 'post' ) );
    }

    public function posts_request( $request )
    {
        remove_filter( current_filter(), array( $this, __FUNCTION__ ), PHP_INT_MAX  );

        // Collect the generated SQL for each sub-query:
        foreach( (array) $this->args['args'] as $a )
        {
            $q = new WP_Query_Empty( $a, $this->args['sublimit'] );
            $this->sub_sql[] = $q->get_sql();
            unset( $q );
        }

        // Combine all the sub-queries into a single SQL query.
        // We must have at least two subqueries:
        if ( count( $this->sub_sql ) > 1 )
        {
            $s = '(' . join( ') UNION (', $this->sub_sql ) . ' ) ';

            $request = sprintf( "SELECT SQL_CALC_FOUND_ROWS * FROM ( $s ) as combined LIMIT %s,%s",
                $this->args['posts_per_page'] * ( $this->args['paged']-1 ),
                $this->args['posts_per_page']
            );          
        }
        return $request;
    }

} // end class

/**
 * Class WP_Query_Empty
 *
 * @link https://stackoverflow.com/a/23704088/2078474
 */

class WP_Query_Empty extends WP_Query 
{
    protected $args      = array();
    protected $sql       = '';
    protected $limits    = '';
    protected $sublimit  = 0;

    public function __construct( $args = array(), $sublimit = 1000 )
    {
        $this->args     = $args;
        $this->sublimit = $sublimit;

        add_filter( 'posts_clauses',  array( $this, 'posts_clauses' ), PHP_INT_MAX  );
        add_filter( 'posts_request',  array( $this, 'posts_request' ), PHP_INT_MAX  );

        parent::__construct( $args );
    }

    public function posts_request( $request )
    {
        remove_filter( current_filter(), array( $this, __FUNCTION__ ), PHP_INT_MAX );
        $this->sql = $this->modify( $request );             
        return '';
    }

    public function posts_clauses( $clauses )
    {
        remove_filter( current_filter(), array( $this, __FUNCTION__ ), PHP_INT_MAX  );
        $this->limits = $clauses['limits'];
        return $clauses;
    }

    protected function modify( $request )
    {
        $request = str_ireplace( 'SQL_CALC_FOUND_ROWS', '', $request );

        if( $this->sublimit > 0 )
            return str_ireplace( $this->limits, sprintf( 'LIMIT %d', $this->sublimit ), $request );
        else
            return $request;
    }

   public function get_sql( )
    {
        return $this->sql;
    }

} // end class

然后，您可以根据需要调整课程。

我使用技巧mentioned here来保留UNION子查询的顺序。您可以使用我们的sublimit参数相应地修改它。

这也适用于主要查询，例如使用posts_request过滤器。

我希望这会有所帮助。

Answer 2

麻烦在于'order'参数：'meta_query'参数accepts an array of meta queries以及'relation'参数（基本上是“AND”或“OR”）。这可用于选择小于和大于或等于$today的帖子（尽管此时元查询无用，因为它选择每个（“OR”）或不选择（“AND” “）研讨会。不幸的是，WP_Query不允许你任意排序结果（从最近的即将到来的最近的研讨会转换）。

如果您知道如何在MySQL中直接启用此功能，您可以考虑查看the WP_Query filters，特别是posts_orderby filter。这些过滤器使您可以开始使用WP_Query类生成的实际SQL，而无需切换到完全自定义查询。但是，请注意，限制这些过滤器的范围或将其应用于您网站上的每个查询的风险非常重要（posts_where filter documentation有一些很好的示例，说明如何执行此操作）

Wordpress结合查询

2 个答案:

演示＃1：

演示＃2：

演示＃3：

类：