如何将列分割成按日期排序的多个列 [英] How to split a column into multiple columns ordered by date

问题描述

当我尝试以正确的格式获取数据库的数据时，我遇到了很多问题。
我正在寻找以几天的方式打印数据库输出的方式。

I'm having a lot of problems when trying to get the data of my database in a proper format. I'm looking for the way to print the output of my database in columns by days.

我的数据库有两列，一列有一个 timestamp ，格式如 YYYY-MM-DD H：M ，另一个与速度相关的数据的列。

My database has two columns, one with a timestamp in a format like YYYY-MM-DD H:M and another colum with data related to a speed.

我需要按日分列数据列。

I need to split the speed data in columns by day.

或多或少，我的数据库是这样的（with 288数据每天）：

More or less, my database is something like this (with 288 data everyday):

 Timestamp          |   Speed

2014-05-01 00:03:00 |   328.71    
2014-05-01 00:18:00 |   331.31    
2014-05-01 00:33:00 |   193.83        
2014-05-02 00:03:00 |   321.21    
2014-05-02 00:18:00 |   290.39    
2014-05-02 00:33:00 |   283.43

我要找的是：

Hour    | 2014-05-01 | 2014-05-02

00:03:00 | 328.71    | 321.21     
00:18:00 | 331.31    | 290.39    
00:33:00 | 193.83    | 283.43

首先，我试图以静态方式做，但是当我得到它我会做动态的。

First of all, I've tried to do in a static way, but when I get it, I'll do dynamic.

我所做的查询是

SELECT 
(CASE WHEN Timestamp>='2014-05-01' AND Timestamp<='2014-05-03' 
    THEN date_format(Timestamp,'%H:%i') ELSE 0 END) AS 'Hour', 
(CASE WHEN Timestamp>='2014-05-01' AND Timestamp<='2014-05-02' 
    THEN speed ELSE 0 END) AS '2014-05-01', 
(CASE WHEN Timestamp>='2014-05-02' AND Timestamp<='2014-05-03' 
    THEN velocidad ELSE 0 END) AS '2014-05-02' 
FROM `db_speed` 
WHERE Timestamp>='2014-05-01' AND Timestamp<='2014-05-10

有了这个查询，我得到一个这样的结构：

With this query, I get a structure like this:

Hour     | 2014-05-01 | 2014-05-02

00:03:00 | 328.71     | 0     
00:18:00 | 331.31     | 0    
00:33:00 | 193.83     | 0    
00:03:00 | 0          | 321.21     
00:18:00 | 0          | 290.39
00:33:00 | 0          | 283.43

推荐答案

你相当接近，你只是错过 group by 和聚合函数。

You are quite close, you're just missing group by and aggregate function.

SELECT 
(CASE WHEN Timestamp>='2014-05-01' AND Timestamp<='2014-05-03' 
    THEN date_format(Timestamp,'%H:%i') ELSE 0 END) AS 'Hour', 
MAX((CASE WHEN Timestamp>='2014-05-01' AND Timestamp<='2014-05-02' 
    THEN speed ELSE NULL END)) AS '2014-05-01', 
MAX((CASE WHEN Timestamp>='2014-05-02' AND Timestamp<='2014-05-03' 
    THEN speed ELSE NULL END)) AS '2014-05-02' 
FROM `db_speed` 
WHERE Timestamp>='2014-05-01' AND Timestamp<='2014-05-10'
GROUP BY `Hour`

• 看到它在一个 sqlfiddle


• see it working live in an sqlfiddle

这篇关于如何将列分割成按日期排序的多个列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！