在查询期间设置变量答案

【问题标题】：Set variable during a query在查询期间设置变量
【发布时间】：2019-02-20 12:56:23
【问题描述】：

有以下查询

SELECT 
Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date',
device_serial as "Device Serial",
customer_name as "Customer",
error_code as 'Error Code',
resolutiom as 'Resolution'
FROM preventive_maintenance
ORDER BY `timestamp` desc
LIMIT 25

我想按随机的“截止日期”订购，我该怎么做？

【问题讨论】：

标签： mysql grafana

【解决方案1】：

只需将当前查询设为子查询即可。

SELECT 
    T.*
FROM
    (SELECT 
        Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as `Due Date`,
        device_serial as `Device Serial`,
        customer_name as `Customer`,
        error_code as `Error Code`,
        resolutiom as `Resolution`
    FROM preventive_maintenance
        -- ORDER BY `timestamp` desc
    LIMIT 25) AS T
ORDER BY T.`Due Date`

【讨论】：

在 ORDER BY 中出现了问题，我希望最近的日子排在首位
@user829174 你的as 'due date' 在 sql 中不正确。字段名称必须封装在 ``not " 或 ' 中。请参阅编辑
当复制/粘贴到 Grafana 时，我得到：错误 1064：您的 SQL 语法有错误；检查与您的 MySQL 服务器版本相对应的手册，以在第 6 行的“客户，error_code 作为错误代码，resolutiom 作为“Resolutio”附近使用正确的语法
@user829174 在as customer 之后缺少一个`。你应该能够发现像这样的简单错误:)
在工作台中粘贴时，结果显示效果很好。当粘贴到 grafana 结果的顺序不正确时......你有什么想法吗？

【解决方案2】：

Order By `Due Date`

需要工作。你试过了吗？如果没有，您可以使用子查询。

SELECT * FROM 
(
    SELECT 
      Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date',
      device_serial as "Device Serial",
      customer_name as "Customer",
      error_code as 'Error Code',
      resolutiom as 'Resolution'
    FROM preventive_maintenance
) T
ORDER BY `Due Date`
LIMIT 25

示范

SELECT * from (
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
union all 
SELECT  Now() + INTERVAL FLOOR(RAND()*(1000-5+1)+5) DAY as 'Due Date' from dual
) T
order by `Due Date`
LIMIT 5

|截止日期 | | :----------------- | | 2019-10-27 13:16:15 | | 2019-11-26 13:16:15 | | 2020-05-05 13:16:15 | | 2020-07-01 13:16:15 | | 2020-07-01 13:16:15 |

db小提琴here

【讨论】：

在 ORDER BY 中出现了问题，我希望最近的日子排在首位
是否可以创建示例小提琴来演示dbfiddle.uk 上的问题？
它在小提琴中效果很好，我正在使用 Grafa，问题可能是“到期日期”是一个字符串吗？