将 ORDER BY 与已有 GROUP BY 的查询一起使用

发布于 2024-11-29 11:09:06 字数 409 浏览 1 评论 0原文

我正在使用 MySQL，并且我有一个表，其中有一列包含日期（我正在制作一个课程的截止日期表）。以前我的查询如下：

SELECT * FROM duedates_f2011 ORDER BY anothercolumn

为了防止重复出现（基于截止日期列），我必须将其更改如下：

SELECT * FROM duedates_f2011 GROUP BY duedate

目前，它保留相同的顺序，但如何确保它仍然会这样做？我读过的 GROUP BY 教程中没有任何内容表明它仍然会对它进行排序，并且随后添加 ORDER BY 语句是不正确的。是否有我遗漏的东西，或者我应该添加其他东西以确保它保持秩序？

（如我的标签所示，我正在使用 PHP 来运行查询）

原文

I'm using MySQL and I have a table that has dates in a column (I'm making a table of due dates for a class). Previously I had the query as follows:

SELECT * FROM duedates_f2011 ORDER BY anothercolumn

In order to prevent duplicate occurrences (based on the duedate column) I had to change it as follows:

SELECT * FROM duedates_f2011 GROUP BY duedate

Currently, it's retained the same order, but how can I assure that it will still do so? Nothing in the GROUP BY tutorials I've read indicates that it will still sort it, and adding an ORDER BY statement afterwards is incorrect. Is there something I'm missing, or is there something else I should add to make sure it remains in order?

(as indicated in my tags, I'm using PHP to run the query)

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时间海 2024-12-06 11:09:06

SELECT * FROM duedates_f2011 GROUP BY duedate ORDER BY anothercolumn;

这是根据 MySQL 手册页。

SELECT * FROM duedates_f2011 GROUP BY duedate ORDER BY anothercolumn;

This is according to the MySQL manpages.

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北城挽邺 2024-12-06 11:09:06

先分组选择，然后再排序怎么样？

SELECT * FROM
   (SELECT * FROM duedates_f2011 GROUP BY duedate) a
ORDER BY anothercolumn

我认为您没有任何理由决定按分组列对其进行排序。大胆！对数据库的要求更高！它应该屈服于你的每一个突发奇想！

mysql> SELECT Jump FROM YourDatabase;
+----------------+ 
| Jump           |
+----------------+
| How high?      |
+----------------+
1 row in set (0.00 sec)

How about selecting with a grouping first, then doing the order later, like this?

SELECT * FROM
   (SELECT * FROM duedates_f2011 GROUP BY duedate) a
ORDER BY anothercolumn

I don't see any reason for you to settle on it being ordered by the grouped column. Be bold! Demand more of your database! It should bow to your every whim!

mysql> SELECT Jump FROM YourDatabase;
+----------------+ 
| Jump           |
+----------------+
| How high?      |
+----------------+
1 row in set (0.00 sec)

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