SQL Wordpress查询-内部与外部联接

Question

我正在尝试获取wp_postmeta表具有的所有帖子(meta_key='propdetails' AND meta_value LIKE '%Vacant Unrented Ready%')或(meta_key='featured' AND meta_value='on') 。

我现有的查询（下面）正在工作，除非meta_key“功能”行丢失 。 然后，该帖子不会返回。

类似地，对于匹配行，我还需要检索我想获取meta_value ，其中meta_key='martygeocoderlatlng' 。 但是，如果缺少meta_key，则整个帖子都不会返回。

因此，我需要使用现有查询并使meta_key='featured'或meta_key='martygeocoderlatlng'可选，因此，如果不存在它们，我仍然可以进行其他比较并获取所需的数据。

（我认为可以通过某种方式使用OUTER JOIN来完成，但是我不能完全弄清语法。）

这是我现有的查询，该查询仅返回wp_postmeta表中的meta_key ='featured'和meta_key ='martygeocoderlatlng'存在的行（当然，还满足WHERE子句中的其他条件）：

SELECT 
    p.*,
    pm.*,
    pm_featured.meta_value AS featured,
    pm_latlng.meta_value AS latlng

FROM 
    wp_posts p
    JOIN wp_postmeta pm
      ON pm.post_id = p.ID
    JOIN wp_postmeta pm_propdetails
      ON (pm_propdetails.post_id = p.ID AND pm_propdetails.meta_key = 'propdetails')
    JOIN wp_postmeta pm_featured
      ON (pm_featured.post_id = p.ID AND pm_featured.meta_key = 'featured-property')
    JOIN wp_postmeta pm_latlng
      ON (pm_latlng.post_id = p.ID AND pm_latlng.meta_key = 'martygeocoderlatlng')

    JOIN wp_term_relationships tr
      ON tr.object_id = p.ID
    JOIN wp_term_relationships tr_taxrel
      ON (tr_taxrel.object_id = p.ID AND tr_taxrel.term_taxonomy_id = 12)

WHERE
    (pm_propdetails.meta_value LIKE '%Vacant Unrented Ready%'
        OR
     pm_featured.meta_value = 'on')

    AND p.post_type = 'property'
    AND p.post_status = 'publish'

GROUP BY p.ID
ORDER BY p.post_date DESC

Answer 1

这是一个非常激烈的查询。 在不更好地了解表结构的情况下，很难确切地知道如何有效地执行此操作（似乎可以合并其中的一些JOINS）。

这只是编辑原始查询的一个刺：

SELECT 
    p.*,
    pm.*,
    pm_featured.meta_value AS featured,
    pm_latlng.meta_value AS latlng

FROM 
    wp_posts p
    JOIN wp_postmeta pm
      ON pm.post_id = p.ID
    JOIN wp_postmeta pm_propdetails
      ON (pm_propdetails.post_id = p.ID AND pm_propdetails.meta_key = 'propdetails')
    LEFT JOIN wp_postmeta pm_featured
      ON (pm_featured.post_id = p.ID AND pm_featured.meta_key = 'featured-property')
    LEFT JOIN wp_postmeta pm_latlng
      ON (pm_latlng.post_id = p.ID AND pm_latlng.meta_key = 'martygeocoderlatlng')

    JOIN wp_term_relationships tr
      ON tr.object_id = p.ID
    JOIN wp_term_relationships tr_taxrel
      ON (tr_taxrel.object_id = p.ID AND tr_taxrel.term_taxonomy_id = 12)

WHERE
    (pm_propdetails.meta_value LIKE '%Vacant Unrented Ready%'
        OR
     (pm_featured.meta_value = 'on' OR pm_feature.meta_value IS NULL))

    AND p.post_type = 'property'
    AND p.post_status = 'publish'

GROUP BY p.ID
ORDER BY p.post_date DESC

它只是使用LEFT JOIN尝试返回可能缺少meta_key的帖子，然后修改了WHERE部分以尝试说明pm_featured.meta_value是否为NULL。

如果您提供更多信息，可以尝试其他版本。

编辑：根据您的问题，这可能也可以。 真的只是黑暗中的一枪而已=）

SELECT T2.*, T1.featured, T1.latlng FROM
(
    SELECT post_id, SUM(IF((meta_key='propdetails' AND meta_value LIKE '%Vacant Unrented Ready%') OR ((meta_key='featured' AND meta_value='on')),1,0)) AS Keeper
    , MAX(IF(meta_key = 'featured-property',meta_value,NULL)) AS featured
    , MAX(IF(meta_key = 'martygeocoderlatlng',meta_value,NULL)) AS latlng
    FROM wp_postmeta 
    GROUP BY post_id
    HAVING Keeper>0
) AS T1
JOIN
wp_posts AS T2
ON T1.post_id=T2.ID
AND T2.post_type = 'property'
AND T2.post_status = 'publish'
JOIN
wp_term_relationships AS T3
ON T2.ID=T3.object_id AND T3.term_taxonomy_id = 12
GROUP BY T2.ID
ORDER BY T2.post_date DESC

自从第二个查询结束工作（有点令人惊讶，我做了很多假设；）之后，这个查询应该会更快一点，更容易理解...（注意：尤其是当您在（ meta_key ， meta_value ）在wp_postmeta表中。）

SELECT T2.*, T1.featured, T1.latlng FROM
(
    SELECT postmetas_info.post_id
    , MAX(IF(meta_key = 'featured-property',meta_value,NULL)) AS featured
    , MAX(IF(meta_key = 'martygeocoderlatlng',meta_value,NULL)) AS latlng
    FROM 
    (
        SELECT DISTINCT post_id FROM wp_postmeta WHERE (meta_key='propdetails' AND meta_value LIKE '%Vacant Unrented Ready%') OR (meta_key='featured' AND meta_value='on')
    ) AS postmetas_applicable
    JOIN
    wp_postmeta AS postmetas_info
    ON postmetas_applicable.post_id=postmetas_info.post_id
    GROUP BY postmetas_info.post_id
) AS T1
JOIN
wp_posts AS T2
ON T1.post_id=T2.ID
AND T2.post_type = 'property'
AND T2.post_status = 'publish'
JOIN
wp_term_relationships AS T3
ON T2.ID=T3.object_id AND T3.term_taxonomy_id = 12
GROUP BY T2.ID
ORDER BY T2.post_date DESC

上一个查询中的SUM（IF（））很有趣，但可能不如预期的那样有效，因为它会评估表中的每一行。 上面的查询首先减少了post_id的内容，然后仅基于符合条件的post_id的内容获取相应的数据。