在使用SQL创建查询时需要帮助吗？ [英] Need some help in creating a query in SQL?

问题描述

ID|message| UpdateTime| TicketID| StaffID

10008;"Yes, it is!";"2012-04-15 16:15:00";1008;660
10013;"Thanks for swift reply!";"2012-04-15 17:15:00";1008;660

CAn您告诉我什么时候写下这两个查询：

CAn u tell me when I write these 2 queries :

Select MAX(UpdateTime) from TicketUpdate where ticketUpdate.id = 10008;    
Select MIN(UpdateTime) from TicketUpdate where ticketUpdate.id = 10008;

即使在我的数据库中有两次不同的时间，输出也一样。
您能告诉我这里是什么问题吗？

The output the same even in my database if have 2 different times. Can u tell me what could be the problem here?

推荐答案

ID 似乎是此表的唯一标识符。相反，您似乎想使用 TicketID 来查找每张票证的最大值和最小值。

ID appears to be the unique identifier for this table. Instead, it looks like you want to use TicketID to find the max and min values per ticket.

例如，以找到 TicketID = 1008 的

SELECT MAX(UpdateTime) FROM TicketUpdate WHERE TicketUpdate.TicketID = 1008;    
SELECT MIN(UpdateTime) FROM TicketUpdate WHERE TicketUpdate.TicketID = 1008;

或在一个查询中：

SELECT 
  MAX(UpdateTime) AS newest,
  MIN(UpdateTime) AS oldest
FROM TicketUpdate
WHERE TicketID = 1008;

要获取每个TicketID的最新信息和最旧信息，请使用 GROUP BY 并省略 WHERE 子句。：

To get the most recent and oldest for every individual TicketID, use a GROUP BY and omit the WHERE clause.:

SELECT 
  TicketID,
  MAX(UpdateTime) AS newest,
  MIN(UpdateTime) AS oldest,
FROM TicketUpdate
GROUP BY TicketID

如果使用 ID 查询，则由于每个唯一标识其行的 ID 似乎只有一个值。

If you query using ID, you will always get the same row since there appears to be only one value for each ID that uniquely identifies its row.

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