我认为您的问题是，当您使用max（）时，您的子选择只生成一行，而每个项目需要一行（我认为是lg\u pj\u id）。
只需重写subselect就可以为每个项目生成一行，其中包含来自最近活动的信息。您的操作日志中是否有活动id？因为它看起来像lg\u pj\u id是项目的\u id。lg\u desc的含义也是未知的（或者是动作的\u log\u id？）。在子选择中尝试按项目id分组，并根据需要从相应行中选择最大值或选择每个组具有最大值的行（项目id）
感谢小组的建议，让每个项目一行。我尝试更改子查询，如下所示：

SELECT MAX(lg_id) AS MaxLogID, lg_desc, lg_pj_id
    FROM PL_LOG PL
    GROUP BY lg_pj_id

现在，我从日志中得到一行，但是它给了我max id，但不是同一行的lg\u desc！如果我单独尝试子查询：

SELECT lg_id, lg_pj_id, lg_date, lg_desc 
    FROM `PL_LOG` 
    WHERE lg_pj_id = 33 
    ORDER BY lg_date DESC

我有这些排。你可以看到最大行，68有一个描述“30分钟skype通话。”

68,33,2018-06-10 00:00:00","30 minute skype call."

61,33,"2018-06-02 00:00:00","Sent email to try to elicit a response."

52,33,"2018-05-10 00:00:00","sent follow up email"

47,33,"2018-03-26 00:00:00","sent initial email"

46,33,"2018-03-26 00:00:00","sent initial email"

但是，当我尝试使用group by仅获取该行时，它会给出max lg\u id，但会给出第一个lg\u desc。我需要来自max（lg\u id）行的所有数据：

SELECT MAX(lg_id) AS MaxLogID, lg_pj_id, lg_date, lg_desc
    FROM PL_LOG
    WHERE lg_pj_id = 33
    GROUP BY lg_pj_id
    ORDER BY MaxLogID DESC

退货：

68, 33, "2018-03-26 00:00:00", "sent initial email"

试试我评论中提到的这个：

SELECT 
PJ.pj_id, PJ.pj_title, PJ.pj_location, PJ.pj_desc, PJ.pj_request,    
PJ.pj_date_start, PP1.pp_name AS supervisor_name, PP2.pp_name AS 
customer_name, ST.st_desc, logDate, logDesc

FROM PL_PROJECTS PJ 

INNER JOIN PL_PEOPLE PP1 ON PJ.pj_spst_member = PP1.pp_id 

INNER JOIN PL_PEOPLE PP2 ON PJ.pj_pp_id = PP2.pp_id 

INNER JOIN PL_STATUS ST ON PJ.pj_status = ST.st_id 

LEFT JOIN (SELECT lg_id, lg_date AS logDate, lg_desc AS logDesc, lg_pj_id  
           FROM PL_LOG AS PL 
           WHERE PL.lg_id=(SELECT MAX(lg_id) FROM PL_LOG AS PL_2
                           WHERE PL_LOG.lg_pj_id  = PL_2.lg_pj_id )
LR ON LR.lg_pj_id = PJ.pj_id

GROUP BY PJ.pj_id
ORDER BY logDate DESC

LIMIT 9999999