我有以下查询不返回结果：
1. SELECT *
2. FROM wp_postmeta pm
3. LEFT JOIN wp_posts p ON (p.ID = pm.post_id)
4. LEFT JOIN wp_term_relationships tr ON (p.ID = tr.object_id)
5. LEFT JOIN wp_term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id)
6. WHERE p.post_status = 'publish'
7. AND p.post_type = 'post'
8. AND p.post_date < NOW()+INTERVAL 1 DAY
9. AND tt.taxonomy = 'category'
10. AND tt.term_id IN(3)
11. AND (pm.meta_key = 'EndDate' AND pm.meta_value > DATE_ADD(NOW(), INTERVAL 3 HOUR))
12. AND (pm.meta_key = 'NumPrizes' AND pm.meta_value > 1)
13. GROUP BY ID
14. ORDER BY p.ID DESC
出现此问题是由于第 11 行和第 12 行。我可以删除一个或另一个并获得结果，但我需要两者才能得到我想要的东西。
我想要的是获得pm.meta_key EndDate 大于今天和 pm.meta_key NumPrizes 大于 0 的结果。
这个想法是输出数据库中的奖品总数。
数据库是由wordpress构建的，所以我无法更改它。它的工作方式是meta_key有一个值，该值是字段的名称，meta_value是meta_key的实际值。
wp_postmeta表示例：
meta_id post_id meta_key meta_value
1 45 EndDate 2012-01-01 <- too old
2 45 NumPrizes 5 <- since too old, don't count
3 76 EndDate 2012-07-03 <- valid date but...
4 76 NumPrizes 1 <- only 1 prize so don't count
5 90 EndDate 2012-06-02 <- valid date and
6 90 NumPrizes 4 <- more than one prize so count it
7 192 EndDate 2012-09-01 <- valid date and
8 192 NumPrizes 9 <- more than one prize so count it
预期产出：奖项数量为13个。（4+9 = 13）。
谁能指出我正确的方向？
当然，单个列不可能一次采用两个不同的值：
11. AND pm.meta_key = 'EndDate' <<-- big error: column can't take two 12. AND pm.meta_key = 'NumPrizes' <<-- differents values at a time
您应该规范化表和/或编写正确的查询：
1. SELECT *
2. FROM wp_postmeta pm
3. LEFT JOIN wp_posts p ON (p.ID = pm.post_id)
4. LEFT JOIN wp_term_relationships tr ON (p.ID = tr.object_id)
5. LEFT JOIN wp_term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id)
6. WHERE p.post_status = 'publish'
7. AND p.post_type = 'post'
8. AND p.post_date < NOW()+INTERVAL 1 DAY
9. AND tt.taxonomy = 'category'
10. AND tt.term_id IN(3)
11. AND (pm.meta_key = 'EndDate' AND pm.meta_value > DATE_ADD(NOW(), INTERVAL 3 HOUR))
12. AND exists (
select 1 from wp_postmeta pm2 where
pm2.post_id = pm.post_id and
pm2.meta_key = 'NumPrizes' AND pm2.meta_value > 1
)
13. GROUP BY ID
14. ORDER BY p.ID DESC
编辑
乔纳森，我不知道您的检查结果，因为有问题时您谈论的是单个标量结果（数字 13），但在查询中您将主表与其他表联接。我希望我在这里编写的这段代码可以对您有所帮助，但您应该根据自己的具体情况对其进行调整。
1. SELECT *, sum( __your_prizes_agrregation__ )
2. FROM wp_postmeta pm
3. LEFT JOIN wp_posts p ON (p.ID = pm.post_id)
4. LEFT JOIN wp_term_relationships tr ON (p.ID = tr.object_id)
5. LEFT JOIN wp_term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id)
6. WHERE p.post_status = 'publish'
7. AND p.post_type = 'post'
8. AND p.post_date < NOW()+INTERVAL 1 DAY
9. AND tt.taxonomy = 'category'
10. AND tt.term_id IN(3)
11. AND exists (
select 1 from wp_postmeta pm2 where
pm2.post_id = pm.post_id and
pm2.meta_key = 'EndDate' AND
pm2.meta_value > DATE_ADD(NOW(), INTERVAL 3 HOUR)
)
12. AND exists (
select 1 from wp_postmeta pm2 where
pm2.post_id = pm.post_id and
pm2.meta_key = 'NumPrizes' AND pm2.meta_value > 1
)
13. GROUP BY ID
14. ORDER BY p.ID DESC