我也遇到过类似的问题

子查询和加入救援

SELECT p."Date"
        ,p."Symbol"
        ,p."ratio_roll_qtr_ret"
    FROM PUBLIC."prices_vw" AS p
    JOIN (
        SELECT "Symbol"
            ,max("Date")
        FROM PUBLIC."prices_vw"
        GROUP BY "Symbol"
        ) AS sq ON p."Date" = sq."max"
        AND p."Symbol" = sq."Symbol"
    WHERE p."ratio_roll_qtr_ret" IS NOT NULL
    ORDER BY "ratio_roll_qtr_ret" DESC;

试试这个:

SELECT jos_categories.title AS name,
       joined .catid,
       joined .title,
       joined .introtext
FROM   jos_categories
       INNER JOIN (SELECT *
                   FROM   (SELECT `title`,
                                  catid,
                                  `created`,
                                  introtext
                           FROM   `jos_content`
                           WHERE  `sectionid` = 6
                           ORDER  BY `id` DESC) AS yes
                   GROUP  BY `yes`.`catid` DESC
                   ORDER  BY `yes`.`created` DESC) AS joined
         ON( joined.catid = jos_categories.id )  

我还没有测试大DB，但我认为这可能比连接表更快:

SELECT *, Max(Id) FROM messages GROUP BY Name

Hi @Vijay Dev如果你的表消息包含Id，这是自动增加主键，然后在主键上获取最新的记录，你的查询应该如下所示:

SELECT m1.* FROM messages m1 INNER JOIN (SELECT max(Id) as lastmsgId FROM messages GROUP BY Name) m2 ON m1.Id=m2.lastmsgId

你可以通过计数来分组，也可以得到分组的最后一项，比如:

SELECT 
    user,
    COUNT(user) AS count,
    MAX(id) as last
FROM request 
GROUP BY user

是什么:

select *, max(id) from messages group by name 

我已经在sqlite上测试了它，它返回所有列和所有名称的最大id值。