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谈到 SQL，我还是个新手，上周工作中遇到了一个问题。我能够通过 RoR 查询来克服它，并根据我的需要重新格式化数据（混乱的 D：）；但是，我真的很想知道sql的解决方案，如果有的话

我有一个看起来像这样的 MySQL 数据库

| id | unique_visitors |      time_period    |
| 1  |              16 | 2013-07-01 00:00:00 |
| 2  |              20 | 2013-07-01 01:00:00 |
| 3  |               2 | 2013-07-01 02:00:00 |

我需要的最终输出如下所示

|    date    | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 |.... | 22 | 23|
| 2013-07-01 | 16 | 20 |  2 | 32 | .........

每行将显示日期，以及每小时的唯一访客。

我不确定这是否可以通过 sql 查询实现，并且真的很想借此机会学习一些东西。

谢谢 SQL 大师！

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1 回答 1

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CASE 语句会变得复杂，但在这里。睡前感觉像是一个挑战

表统计信息（id、unique_visitors、time_period）

select DATE_FORMAT(time_period ,'%Y-%m-%d') as date, 
sum(CASE WHEN EXTRACT(hour from time_period)  =  00 THEN unique_visitors ELSE  0 END) as '00', 
sum(CASE WHEN EXTRACT(hour from time_period)  =  01 THEN unique_visitors ELSE  0 END) as '01', 
sum(CASE WHEN EXTRACT(hour from time_period)  =  02 THEN unique_visitors ELSE  0 END) as '02',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  03 THEN unique_visitors ELSE  0 END) as '03',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  04 THEN unique_visitors ELSE  0 END) as '04',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  05 THEN unique_visitors ELSE  0 END) as '05',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  06 THEN unique_visitors ELSE  0 END) as '06',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  07 THEN unique_visitors ELSE  0 END) as '07',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  08 THEN unique_visitors ELSE  0 END) as '08',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  09 THEN unique_visitors ELSE  0 END) as '09',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  10 THEN unique_visitors ELSE  0 END) as '10',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  11 THEN unique_visitors ELSE  0 END) as '11',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  12 THEN unique_visitors ELSE  0 END) as '12',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  13 THEN unique_visitors ELSE  0 END) as '13',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  14 THEN unique_visitors ELSE  0 END) as '14',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  15 THEN unique_visitors ELSE  0 END) as '15',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  16 THEN unique_visitors ELSE  0 END) as '16',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  17 THEN unique_visitors ELSE  0 END) as '17',   
sum(CASE WHEN EXTRACT(hour from time_period)  =  18 THEN unique_visitors ELSE  0 END) as '18',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  19 THEN unique_visitors ELSE  0 END) as '19',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  20 THEN unique_visitors ELSE  0 END) as '20',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  21 THEN unique_visitors ELSE  0 END) as '21',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  22 THEN unique_visitors ELSE  0 END) as '22',  
sum(CASE WHEN EXTRACT(hour from time_period)  =  23 THEN unique_visitors ELSE  0 END) as '23' 
from stats
group by date
order by date

输出

      date  00  01  02  03  04  05  06  07  08  09  10  11  12  13 14  15  16  17  18  19  20  21  22  23
2013-07-01  22  16  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
2013-07-02  0   0   0   0   30  0   0   0   50  0   0   0   0   0   0   0   15  0   0   0   0   0   0   0

——杰夫·韦斯

于 2013-07-27T05:20:27.010 回答