我有以下查询,该查询不返回结果:

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


由于第11行和第12行,出现了问题。我可以删除一个或另一个并获得结果,但是为了获得想要的东西,我需要两者。

我想要得到的结果是pm.meta_key EndDate大于今天,而pm.meta_key NumPrizes大于0。

想法是在数据库中输出奖品总数。

该数据库是由wordpress构建的,因此无法更改。它的工作方式是meta_key具有一个值,该值是字段的名称,meta_value是meta_key的实际值。

wp_postmeta表的示例:

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:奖品数量为13。(4 + 9 = 13)。

谁能指出我正确的方向?

最佳答案

当然,单个列不可能一次取两个差值:


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


已编辑

乔纳森(Jonathan),我不知道您所期望的结果,因为有疑问您谈论的是单个标量结果(数字13),但是在查询中将主表与其他表连接在一起。我希望我在这里编写的这段代码可以为您提供帮助,但是您应该根据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

09-10 11:43
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