MySQL将子查询转换为联接

是否可以将此子查询转换为join

SELECT  `news`.`newsId`,
        (SELECT `comments`.`text` 
         FROM   `comments`   
         WHERE `comments`.`newsId` = `news`.`newsId` 
         order by `comments`.`date` desc 
         limit 1)   
FROM     `news` , `comments` 
where    `news`.`newsId` = `comments`.`newsId`   
GROUP BY `news`.`newsId` 
order by news.date desc;

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我认为你想做的是：

SELECT n.newsId FROM news n
INNER JOIN comments c ON c.newsId = n.newsId
ORDER BY c.date DESC, n.date
LIMIT 1

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分组依据不是必需的，因为您没有使用任何聚合函数。您可以使用独特的

条目，我假设

newsId

是唯一的

SELECT  `news`.`newsId`,
        `comments`.`text`   
FROM     `news`
CROSS APPLY (SELECT `comments`.`text` 
             FROM   `comments`   
             WHERE `comments`.`newsId` = `news`.`newsId` 
             order by `comments`.`date` desc 
             limit 1) cm  
order by news.date desc;

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你试过什么？你有我们的数据吗？