mysql - mysql查询中orderby的混淆

Question

下面是mysql查询:

SELECT * FROM `is_product_info` ORDER BY (select distinct product_id from is_product_images where is_product_images.product_id = is_product_info.id) asc

我不明白 order by 是如何与子查询一起工作的。

我在 WordPress 插件中遇到过这样的带有 order by 和子查询的查询。这对我来说是新的，所以我想问其他人是否知道这一点。下面是这样的例子:

SELECT wp22_posts.* 
  FROM wp22_posts 
  LEFT 
  JOIN wp22_term_relationships 
    ON wp22_posts.ID = wp22_term_relationships.object_id
 WHERE 1=1 
   AND wp22_posts.ID IN(260,412,413,414,415,469,474,483
                       ,485,487,488,515,516,563,568‌​,569
                       ,584,592,593,596‌​,599,601,604,610
                       ,612‌​,672,675,678,681,690‌​,860,861,862,863)
 GROUP 
    BY wp22_posts.ID 
 ORDER 
    BY (SELECT distinct meta_value from wp22_postmeta where'meta_key' LIKE 'price') ASC 
 LIMIT 0, 10

有人描述这个查询吗？

Answer 1

为了回答您的问题，ORDER BY 子句根本不执行任何操作(除了可能阻止查询工作之外)。