Question

我在SQL Server数据库中有一个表，它每天存储历史数据。结构如下所示：

UploadDate    TypeID    Value1   Value2
-------------------------------------------
2012-01-08    1         NEG      1998-02-05
2012-01-08    2         NEG      1999-02-09
2012-01-08    3         STABLE   1997-02-06
2012-02-08    1         NEG      1998-02-05
2012-02-08    2         NEG      1999-02-09
2012-03-08    1         POS      2012-03-08
2012-03-08    2         STABLE   2012-01-08

正如您在上面看到的TypeID 1＆amp; 2，Value1和Value2已于2012-03-08更改

我的要求是，我必须只显示那些从以前的值改变的行。

在这种情况下，TypeID 1＆amp; 2已经改变，它应该显示当前和最接近的先前值。对于TypeID 3，因为它没有改变，它只会显示最新的值。结果集如下所示：

UploadDate    TypeID    Value1   Value2
-------------------------------------------
2012-01-08    3         STABLE   1997-02-06
2012-02-08    1         NEG      1998-02-05
2012-02-08    2         NEG      1999-02-09
2012-03-08    1         POS      2012-03-08
2012-03-08    2         STABLE   2012-01-08

知道如何使用SQL解决这个问题吗？

Answer 1

Uninspired版本在有序集上使用自联接来检查同一typeid的按时间顺序排列的前一行的值。如果没有前一行或值不同，则输出该行。

; with numbered as (
  select *,
         row_number() over (order by typeid, uploaddate) rn
    from table1
)
select n1.*
  from numbered n1
  left join numbered n2
    on n1.TypeID = n2.TypeID
   and n1.rn + 1 = n2.rn
 where (n2.rn is null 
    or n1.value1 <> n2.value1
    or n1.value2 <> n2.value2)
 order by typeid, uploaddate

Here is Sql Fiddle with example

更新：另一种不需要自联接但需要分组的变体。同一typeid的每个时间轴，value1和value2都被赋予唯一的group_number，稍后将用于提取该组的max（uploaddate）。

; with numbered as (
  select *,
         row_number() over (order by typeid, uploaddate)
       - row_number() over (partition by typeid, value1, value2 
                            order by uploaddate) group_number
    from table1
)
select max(uploaddate) uploaddate, typeid, value1, value2
  from numbered
group by typeid, value1, value2, group_number
order by typeid, uploaddate

Another Sql Fiddle

用于显示数据更改历史记录的SQL查询

1 个答案: