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我正在尝试从两个表中列出最新更新doc_to_do，doc_bug_tracker下面是我的表结构

doc_to_do 在此处输入图像描述

doc_bug_tracker 在此处输入图像描述

这是我当前的查询：

$sth = $this->db->prepare('SELECT p.*, 
        dtd.projects_id as dtd_projects_id, dtd.content as dtd_content, dtd.date_modified as dtd_date_modified,
        dbt.projects_id as dbt_projects_id, dbt.content as dbt_content, dbt.date_modified as dbt_date_modified 
        FROM `projects` p LEFT JOIN `doc_to_do` dtd ON p.id=dtd.projects_id 
        LEFT JOIN `doc_bug_tracker` dbt ON p.id=dbt.projects_id 
        where p.id="'.$project_id.'"');

那么现在如何date_modified从表doc_to_do或订购doc_bug_tracker？

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2 回答 2

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要仅获取最新日期（而不是所有日期，按降序排列），请尝试以下操作：

SELECT
  p.id,
  MAX(GREATEST(dtd.date_modified, dbt.date_modified)) AS MaxDate
FROM projects p
LEFT JOIN doc_to_do dtd ON p.id = dtd.projects_id
LEFT JOIN doc_bug_tracker dbt ON p.id = dbt.projects_id
WHERE p.id = <project_id>
GROUP BY p.id

如果您需要SELECT在GROUP BY.

于 2013-06-19T13:31:07.913 回答
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这应该工作：

'SELECT x.* FROM 
(
    SELECT p.*, 
        dtd.projects_id as dtd_projects_id, dtd.content as dtd_content, dtd.date_modified as dtd_date_modified,
        dbt.projects_id as dbt_projects_id, dbt.content as dbt_content, dbt.date_modified as dbt_date_modified 
        FROM `projects` p LEFT JOIN `doc_to_do` dtd ON p.id=dtd.projects_id 
        LEFT JOIN `doc_bug_tracker` dbt ON p.id=dbt.projects_id 
        where p.id="'.$project_id.'"
) x
ORDER BY x.date_modified ASC'
于 2013-06-19T13:28:27.267 回答