I'm looking for a methodology to compare the difference between 2 rows in the same table. From what I found here ( How to get difference between two rows for a column field? ) it's almost what I wanted. I have done the following code:
create table #tmpTest
(
id_fund int null,
id_ShareType int null,
ValueDate datetime null,
VarNAV float null,
FundPerf float null,
)
insert into #tmpTest(id_fund, id_ShareType, ValueDate, VarNAV)
values(1,1,'20140101',100)
insert into #tmpTest(id_fund, id_ShareType, ValueDate, VarNAV)
values(1,1,'20140102',20)
update #tmpTest
set hrc.FundPerf = (isnull(hrn.VarNAV, 0) - hrc.VarNAV)/hrc.VarNAV
from #tmpTest hrc
left join #tmpTest hrn on hrn.ValueDate = (select min(ValueDate) from #tmpTest where ValueDate > hrc.ValueDate)
and hrc.id_fund = hrn.id_fund and hrc.id_ShareType = hrn.id_ShareType
My issue is that the result I'm computing starts on line 1 instead of line 2.
Hereunder the result I'm obtaining:
id_fund id_ShareType ValueDate VarNAV FundPerf
------- ------------ ------------------- ------- -----------------------------
1 1 2014-01-01 00:00:00 100 -0.8
1 1 2014-01-02 00:00:00 20 -1
whereas I'd like it to be that way:
id_fund id_ShareType ValueDate VarNAV FundPerf
------- ------------ ------------------- ------- -----------------------------
1 1 2014-01-01 00:00:00 100 -1
1 1 2014-01-02 00:00:00 20 -0.8
What's wrong with my approach?
You are not restricting the minimum to the same fund and share type.
update #tmpTest
set hrc.FundPerf = (isnull(hrn.VarNAV, 0) - hrc.VarNAV)/hrc.VarNAV
from #tmpTest hrc left join
#tmpTest hrn
on hrn.ValueDate = (select min(ValueDate)
from #tmpTest tt
where tt.ValueDate > hrc.ValueDate and
hrc.id_fund = tt.id_fund and hrc.id_ShareType = tt.id_ShareType
) and
hrc.id_fund = hrn.id_fund and hrc.id_ShareType = hrn.id_ShareType ;
Try this:
update hrn
set FundPerf = (isnull(hrn.VarNAV, 0) - hrc.VarNAV)/hrc.VarNAV
from #tmpTest hrc
left join #tmpTest hrn on hrn.ValueDate = (select min(ValueDate) from #tmpTest where ValueDate > hrc.ValueDate)
and hrc.id_fund = hrn.id_fund and hrc.id_ShareType = hrn.id_ShareType
Hi you can achieve this using by CTE (Common Table Expression)
create table #tmpTest
(
id_fund int null,
id_ShareType int null,
ValueDate datetime null,
VarNAV float null,
FundPerf float null,
)
insert into #tmpTest(id_fund, id_ShareType, ValueDate, VarNAV)
values(1,1,'20140101',100)
insert into #tmpTest(id_fund, id_ShareType, ValueDate, VarNAV)
values(1,1,'20140102',20)
;With tbl as
( Select Row_Number() OVER (Order by T.ValueDate) as RowNumber,* From #tmpTest T )SELECT Cur.*,(ISNULL(Cur.VarNAV,0) - ISNULL(Prv.VarNAV,0))/Prv.VarNAV as [Col Name] FROM tbl Cur LEFT OUTER JOIN tbl Prv ON Cur.RowNumber = Prv.RowNumber+1 ORDER BY Cur.ValueDate
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