Mysql 选择两个表并按日期排序

我试图列出两个表的最新更新

doc\u to\u do

和

doc\u bug\u tracker

下面是我的表结构

doc\u to\u do

doc\u bug\u跟踪器

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.'"');

那么现在如何按

date\u modified

从表

doc\u to\u do

或

doc\u bug\u tracker

？

这应该可以：

'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'

要仅获取最新日期（与所有日期相反，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

选择
p、 身份证，
最大值（最大值（dtd.date_修改，dbt.date_修改））作为最大值
来自项目p
p.id=dtd.projects\u id上的左JOIN doc\u to\u do dtd
p.id=dbt.projects\u id上的左连接doc\u bug\u tracker dbt
其中p.id=
按p.id分组

如果在

选择中需要其他列，请确保将它们包含在
分组中