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mysql - 从先前查询的结果中提取最新版本的文章

问题描述

我有以下查询：

SELECT e_c.*, c.name, j.status, j.version, j.articleId, j.title FROM assetcategory AS c
    INNER JOIN assetentries_assetcategories AS e_c 
        ON c.categoryId = e_c.categoryId AND c.name = 'news'
    INNER JOIN assetentry AS e
        ON e.entryId = e_c.entryId
    INNER JOIN journalarticle AS j
        ON j.resourcePrimKey = e.classPK
        AND e.classNameId = (SELECT classNameId FROM classname_ WHERE value = 'com.liferay.portlet.journal.model.JournalArticle')
        AND j.companyId= e.companyId
WHERE j.status = 0

它返回news. journalarticles从结果中，我需要为每个articleId. 例如，假设有一篇文章有​​ 4 个版本，即使标题不同，它也是同一篇文章，因为它会有相同的articleId. 因此，对于每个独特的articleId，我需要最新的version. 我怎样才能做到这一点？

标签： mysqlsqldatabaseliferay

解决方案

将连接添加到子查询，以查找每篇文章的最新版本：

SELECT e_c.*, c.name, j1.status, j1.version, j1.articleId, j1.title
FROM assetcategory AS c
INNER JOIN assetentries_assetcategories AS e_c 
    ON c.categoryId = e_c.categoryId AND c.name = 'news'
INNER JOIN assetentry AS e
    ON e.entryId = e_c.entryId
INNER JOIN journalarticle AS j1
    ON j1.resourcePrimKey = e.classPK AND
       e.classNameId = (SELECT classNameId FROM classname_
                   WHERE value = 'com.liferay.portlet.journal.model.JournalArticle') AND
       j.companyId = e.companyId
INNER JOIN
(
    SELECT articleId, MAX(version) AS max_version
    FROM journalarticle
    WHERE status = 0
    GROUP BY articleId
) j2
    ON j1.articleId = j2.articleId AND j1.version = j2.max_version;

加入j2上述别名的子查询背后的基本思想是将结果集限制为每篇文章的最新版本。我们不一定要更改查询的其余部分。

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