Sybase ASE数据分组

Question

我在Sybase ASE中有以下数据

   id   effectiveDate     lastModificationDate  rateValue    
 -----  ----------------  --------------------  ------------ 
 1      20130627          6/27/2013 3:27:09 AM  0            
 1      20130627          6/27/2013 4:39:10 AM  2.75         
 1      20130627          6/28/2013 3:48:15 AM  0            
 1      20130627          6/28/2013 4:36:43 AM  2.75         
 1      20130628          6/28/2013 3:48:14 AM  0            
 1      20130628          6/28/2013 4:36:42 AM  2.75         
 2      20130628          6/28/2013 4:36:42 AM  .75         
 2      20130628          6/28/2013 3:48:14 AM  0            

我如何对它进行分组，这样我就只得到最后一行，即我得到了具有相同id+effectiveDate的最大lastModificationDate的行。

因此，输出将是：

 id     effectiveDate     lastModificationDate  value    
 -----  ----------------  --------------------  ------------ 
 1      20130627          6/28/2013 4:36:43 AM  2.75         
 1      20130628          6/28/2013 4:36:42 AM  2.75         
 2      20130628          6/28/2013 4:36:42 AM  .75         

请注意，这将在TSQL (Sybase ASE 15)上。编辑:已更改数据以使其更逼真

Answer 1

尝试：

SELECT t1.*
FROM Table1 t1
WHERE t1.lastModificationDate  = (SELECT MAX(t2.lastModificationDate)
                                  FROM Table1 t2
                                  WHERE t2.effectiveDate = t1.effectiveDate
                                  AND t2.id = t1.id)

Sybase文档：

子查询可以嵌套在外部select、insert、update或delete语句的where或having子句中，也可以嵌套在另一个子查询或选择列表中。或者，您可以编写许多包含子查询的语句作为连接；Adaptive Server将这类语句处理为连接。

Answer 2

避免使用子查询的另一个答案是...

select id, effectiveDate, lastModificationDate, rateValue 
from #mydata
group by id, effectiveDate
having lastModificationDate = max(lastModificationDate)

如果我假设您的数据存储在#mydata临时表中

create table #mydata(
    id                   int      null,
    effectiveDate        char(8)  null,
    lastModificationDate datetime null,
    rateValue            money    null
)

insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130627", "6/27/2013 3:27:09 AM", 0            
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130627", "6/27/2013 4:39:10 AM", 2.75         
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130627", "6/28/2013 3:48:15 AM", 0            
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130627", "6/28/2013 4:36:43 AM", 2.75         
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130628", "6/28/2013 3:48:14 AM", 0            
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 1, "20130628", "6/28/2013 4:36:42 AM", 2.75         
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 2, "20130628", "6/28/2013 4:36:42 AM", .75         
insert into #mydata(id, effectiveDate, lastModificationDate, rateValue) select 2, "20130628", "6/28/2013 3:48:14 AM", 0