如何在 GROUP BY 和 ORDER BY 中使用多列但只有一列答案

【问题标题】：How to use multiple columns but only one column in GROUP BY and ORDER BY如何在 GROUP BY 和 ORDER BY 中使用多列但只有一列
【发布时间】：2020-11-06 03:39:18
【问题描述】：

我想显示连接表中的多列，但只对group by 和order by 使用一列

我的 PostgreSQL 查询是这样的：

SELECT DISTINCT ON (r.id_rekrutmen)
       r.id_rekrutmen,
       r.judul_rekrutmen,
       rw.tanggal_rekrutmen
FROM rekrutmen r
   INNER JOIN rekrutmen_waktu rw
      ON r.id_rekrutmen = rw.id_rekrutmen
ORDER BY r.id_rekrutmen, rw.tanggal_rekrutmen DESC;

【问题讨论】：

查询看起来没问题；你有什么问题？
我无法像使用该查询的示例图像那样显示，
你的意思是... ORDER BY r.id_rekrutmen DESC, rw.tanggal_rekrutmen DESC; 吗？
我想要 "ORDER BY tanggal_rekrutmen DESC"
那么如果你这样做ORDER BY rw.tanggal_rekrutmen DESC会有什么问题

标签： sql postgresql postgresql-9.1 postgresql-9.2

【解决方案1】：

我想这就是你想要的：

SELECT 
           r.id_rekrutmen,
           r.judul_rekrutmen,
           MAX(rw.tanggal_rekrutmen) AS tanggal_rekrutmen
    FROM rekrutmen r
       INNER JOIN rekrutmen_waktu rw
          ON r.id_rekrutmen = rw.id_rekrutmen
    GROUP BY 
           r.id_rekrutmen,
           r.judul_rekrutmen,

【讨论】：

非常感谢，和我一起工作，SELECT r.id_rekrutmen, r.judul_rekrutmen, MAX(rw.tanggal_rekrutmen) AS tanggal_rekrutmen FROM rekrutmen r INNER JOIN rekrutmen_waktu rw ON r.id_rekrutmen = rw。 id_rekrutmen GROUP BY r.id_rekrutmen, r.judul_rekrutmen ORDER BY tanggal_rekrutmen DESC