Question

我有3张关于投诉的表格。第一个表由抱怨信息本身组成，第二个表是带有status_id的complain_review，第三个表是包含状态信息的status_id表。我正在尝试从抱怨中选择抱怨抱怨，从抱怨请求中选择最新的status_id（按日期排序），并将其与抱怨信息联系起来。

这是我尝试过的（到目前为止没有成功）：

SELECT c1.complain_desc, c2.status_id, c2.name as statusDesc from complain c1 
left join
(SELECT c3.status_id, c4.name, c3.complain_id FROM complain_review c3
inner join complain_status c4 on c4.id=c3.status_id ORDER by c3.date DESC) c2 
on c2.complain_id=c1.id

这是@maheshiv提供的更新示例

..我搜索过该网站，但我不确切知道要搜索的关键字：（

编辑：我在http://sqlfiddle.com/#!9/d86a7a/2建立了一个架构，所以也许有人可以更好地看一下这些表

编辑：也许这将是我能得到的最接近......并且正在工作！

SELECT c.complain_desc, cr1.status_id, cs.name
  FROM complain c
  INNER JOIN complain_review cr1 ON c.id=cr1.complain_id
  INNER JOIN complain_status cs ON cs.id=cr1.status_id
  WHERE cr1.date = (SELECT MAX(cr2.date) FROM complain_review cr2

WHERE cr1.complain_id = cr2.complain_id）

Answer 1

我试图从抱怨中选择抱怨，并从抱怨请求中选择最新的status_id（按日期排序），并将其与抱怨信息联系起来。

这是关于Stack Overflow的一个非常常见的问题。您可以按照greatest-n-per-group找到许多解决方案。

以下是使用您的示例的解决方案：

round

这是一个不使用子查询的不同解决方案：

SELECT c.complain_desc, latest_cr.status_id, cs.name AS status_desc
FROM complain AS c
INNER JOIN (
    SELECT complain_id, status_id 
    FROM (
        SELECT cr.complain_id, cr.status_id, 
          IF(@cgroup=cr.complain_id, @rownum:=@rownum+1, 1) AS rownum,
          (@cgroup:=cr.complain_id)
        FROM (SELECT @cgroup:=0, @rownum:=1) AS _init
        CROSS JOIN complain_review AS cr
        ORDER BY cr.complain_id DESC, cr.date DESC
    ) AS n
    WHERE n.rownum = 1 
) AS latest_cr 
  ON c.id=latest_cr.complain_id
INNER JOIN complain_status AS cs
  ON cs.id = latest_cr.status_id;

Answer 2

我想你可能需要这个查询，我相信max status_id是投诉的最新状态。根据{{3}}

select c1.complain_desc, c2.status_id, c3.name from complain c1 inner join (select complain_id, max(status_id) from complain_review group by complain_id) c2 on c1.id=c2.complain_id inner join complain_status c3 on c3.id=c2.status_id;

子查询和JOIN

2 个答案: