SQL 查询不返回结果

Question

我正在使用三类复选框来过滤来自 WordPress 的帖子（这个问题是关于查询的），并且我知道事实上我应该使用以下查询返回结果（我根据选择的内容自动生成第 7 行在我的过滤器中）：

SELECT * FROM wp_posts 
LEFT JOIN wp_postmeta ON(wp_posts.ID = wp_postmeta.post_id) 
LEFT JOIN wp_term_relationships ON(wp_posts.ID = wp_term_relationships.object_id) 
LEFT JOIN wp_term_taxonomy ON(wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
LEFT JOIN wp_terms ON(wp_terms.term_id = wp_term_taxonomy.term_id) 
WHERE 
    wp_terms.slug IN ('academia') AND wp_terms.slug IN ('early-career') 
    AND wp_term_taxonomy.taxonomy = 'jobtype' 
    AND wp_posts.post_status = 'publish' 
    AND wp_posts.post_type = 'jobs' 
GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC

我至少有 5 个帖子属于 academia 和 early-career 类别。

如果我将第 7 行更改为只有一个 IN 语句，它会很好地过滤一个类别：

wp_terms.slug IN ('academia','journalism') //More than one from same category
AND wp_term_taxonomy.taxonomy = 'jobtype'......

它会找到所有学术或新闻工作（正是我所期望的），但是当我添加另一个 IN 语句时，没有返回任何内容（即使我有符合逻辑的帖子）。

任何人都可以告诉我是否有问题（可能是IN 和值之间的空格？），因为我已经好几天没有运气了。

非常感谢任何帮助！谢谢！

P.S.如果有人想看看这个网站（看看我的意思）：http://www.libertyguide.com/jobs

目前我有一个全局 OR 而不是任何 IN 直到我让它工作。

Answer 1

在IN 子句中指定多个值表示该行必须匹配其中一个值。指定 2 个 IN 子句表明该行必须同时匹配 BOTH，这是不可能的（varchar 不能同时是“学术”和“早期职业”）。

尝试在查询末尾添加以下内容：

HAVING COUNT(*) > [NUMBER OF VALUES SELECTED]

这样就变成了：

SELECT * FROM wp_posts 
LEFT JOIN wp_postmeta ON(wp_posts.ID = wp_postmeta.post_id) 
LEFT JOIN wp_term_relationships ON(wp_posts.ID = wp_term_relationships.object_id) 
LEFT JOIN wp_term_taxonomy ON(wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
LEFT JOIN wp_terms ON(wp_terms.term_id = wp_term_taxonomy.term_id) 
WHERE 
    wp_terms.slug IN ('academia', 'early-career') 
    AND wp_term_taxonomy.taxonomy = 'jobtype' 
    AND wp_posts.post_status = 'publish' 
    AND wp_posts.post_type = 'jobs' 
GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC
HAVING COUNT(*) = 2

Answer 2

SELECT * FROM wp_posts 
LEFT JOIN wp_postmeta ON(wp_posts.ID = wp_postmeta.post_id) 
LEFT JOIN wp_term_relationships ON(wp_posts.ID = wp_term_relationships.object_id) 
LEFT JOIN wp_term_taxonomy ON(wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
LEFT JOIN wp_terms wt1 ON(wt1.term_id = wp_term_taxonomy.term_id) 
LEFT JOIN wp_terms wt2 ON(wt2.term_id = wp_term_taxonomy.term_id) 
WHERE 
   wt1.slug = 'academia' AND wt2.slug = 'early-career' 
    AND wp_term_taxonomy.taxonomy = 'jobtype' 
    AND wp_posts.post_status = 'publish' 
    AND wp_posts.post_type = 'jobs' 
GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC

编辑 要支持 N 个类别，您可以尝试以下操作：

SELECT * FROM wp_posts 
LEFT JOIN wp_postmeta ON(wp_posts.ID = wp_postmeta.post_id) 
LEFT JOIN wp_term_relationships ON(wp_posts.ID = wp_term_relationships.object_id) 
LEFT JOIN wp_term_taxonomy ON(wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) 
WHERE 
    wp_term_taxonomy.taxonomy = 'jobtype' 
    AND wp_posts.post_status = 'publish' 
    AND wp_posts.post_type = 'jobs' 
    AND wp_term_taxonomy.term_id IN (SELECT term_id from wp_terms where slug = 'academia')
    AND wp_term_taxonomy.term_id IN (SELECT term_id from wp_terms where slug = 'early-career')
GROUP BY wp_posts.ID ORDER BY wp_posts.post_date DESC

您可以根据需要在代码中多次添加 AND wp_term_taxonomy... 行。