最近一组SQL入门(Most recent entry in a group SQL)

我有表中，我们可以有同一张票no.for多个entries.i要根据发起了关于列号来获取最新的票（编号相同的票）。

Ticket  VendorTicket  InitiatedOn              Comments
198165  test          2012-08-10 16:31:33.707  test
199485  sagar         2012-08-11 12:36:25.720  sagar
199485  sagar1        2012-08-11 14:36:25.720  sagar1
199478  kishor        2012-08-11 12:37:21.923  kishor

我写了这个查询在T-SQL存储过程中它给了我错误说xObj = {"Incorrect syntax near '.'."}

我的T-SQL

`@SQL='Select ''<a href="javascript:editTicketByIDAction('' + CONVERT(VarChar(Max), Ticket) + '')">'' + CONVERT(VarChar(Max),Ticket) + ''</a>'' t1.Ticket,t1.VendorTicket[Vendor Ticket],t1.Comments 
From VendorTickets t1 
WHERE NotifyOn <= GetDate() And NotifyOn Is Not Null AND 
NOT EXISTS
(SELECT * FROM VendorTickets t2 
WHERE t1.Ticket = t2.Ticket AND t1.InitiatedOn < t2.InitiatedOn)'`

Answer 1:

一般的解决方案（适用于任何数据库）对这个问题如下：

SELECT * FROM [my_table] t1
WHERE NOT EXISTS (
  SELECT * FROM [my_table] t2
  WHERE t1.Ticket = t2.Ticket
  AND t1.InitiatedOn < t2.InitiatedOn
)

这种读取：从MY_TABLE所有值那里是用相同的无人售票Ticket ID和更近的日期。

笔记：

• 这可能会返回重复的情况下，有两个“最近的”入场券具有相同InitiatedOn值。
• 一定要对双方合适的索引Ticket和InitiatedOn列

Answer 2:

尝试这个：

这将给最近的记录各组

select * from  <table> t join
(select Ticket,max(InitiatedOn) as InitiatedOn
from <table>
group by Ticket)a
on t.Ticket=a.Ticket
and t.InitiatedOn=a.InitiatedOn

Answer 3:

SELECT   Ticket,
         VendorTicket,
         InitiatedOn,
         Comments
FROM     (
         SELECT   Ticket,
                  VendorTicket,
                  InitiatedOn,
                  Comments, 
                  ROW_NUMBER() OVER (PARTITION BY Ticket ORDER BY InitiatedOn DESC) AS Row
         FROM     Table
         ) AS Q
WHERE    Q.Row = 1

Answer 4:

如果row_number() over()是供您使用。

select T.Ticket,
       T.VendorTicket,
       T.InitiatedOn,
       T.Comments
from (
     select Ticket,
            VendorTicket,
            InitiatedOn,
            Comments,
            row_number() over(partition by Ticket order by InitiatedOn desc) as rn
     from YourTable
     ) T
where T.rn = 1

Answer 5:

Select t1.* 
from tickets t1 
left join tickets t2 on (t1.ticket = t2.ticket and t2.initiatedon > t1.initiatedon)
where t2.ticket is null;

Answer 6:

select * from table where ticket=199485 order by InitiatedOn desc limit 1;

文章来源: Most recent entry in a group SQL