Subtract nonconsecutive values in same row in t-SQL - sql

Question

I have a data table that has annual data points and quarterly data points. I want to subtract the quarterly data points from the corresponding prior annual entry, e.g. Annual 2014 - Q3 2014, using t-SQL. I have an id variable for each entry, plus a reconcile id variable that shows which quarterly entry corresponds to which annual entry. See below:
CurrentDate PreviousDate Value Entry Id Reconcile Id Annual/Quarterly
9/30/2012 9/30/2011 112 2 3 Annual
9/30/2013 9/30/2012 123 1 2 Annual
9/30/2014 9/30/2013 123.5 9 1 Annual
12/31/2013 9/30/2014 124 4 1 Quarterly
3/31/2014 12/31/2013 124.5 5 1 Quarterly
6/30/2014 3/31/2014 125 6 1 Quarterly
9/30/2014 6/30/2014 125.5 7 1 Quarterly
12/31/2014 9/30/2014 126 10 9 Quarterly
3/31/2015 12/31/2014 126.5 11 9 Quarterly
6/30/2015 3/31/2015 127 12 9 Quarterly
For example, Reconcile ID 9 for the quarterly entries corresponds to Entry ID 9, which is an annual entry.
I have code to just subtract the prior entry from the current entry, but I cannot figure out how to subtract quarterly entries from annual entries where the Entry ID and Reconcile ID are the same.
Here is the code I am using, which is resulting in the right calculation, but increasing the number of results by many rows. I have also tried this as an inner join. I only want the original 10 rows, plus a new difference column:
SELECT DISTINCT T1.[EntryID]
, [T1].[RECONCILEID]
, [T1].[CurrentDate]
, [T1].[Annual_Quarterly]
, [T1].[Value]
, [T1].[Value]-T2.[Value] AS Difference
FROM Table T1
LEFT JOIN Table T2 ON T2.EntryID = T1.RECONCILEID;

Answer 1

Your code should be fine, here's the results I'm getting:
EntryId Annual_Quarterly CurrentDate ReconcileId Value recVal diff
2 Annual 9/30/2012 3 112
1 Annual 9/30/2013 2 123 112 11
9 Annual 9/30/2014 1 123.5 123 0.5
4 Quarterly 12/31/2013 1 124 123 1
5 Quarterly 3/31/2014 1 124.5 123 1.5
6 Quarterly 6/30/2014 1 125 123 2
7 Quarterly 9/30/2014 1 125.5 123 2.5
10 Quarterly 12/31/2014 9 126 123.5 2.5
11 Quarterly 3/31/2015 9 126.5 123.5 3
12 Quarterly 6/30/2015 9 127 123.5 3.5
with your data and this SQL:
SELECT
tr.EntryId,
tr.Annual_Quarterly,
tr.CurrentDate,
tr.ReconcileId,
tr.Value,
te.Value AS recVal,
tr.[VALUE]-te.[VALUE] AS diff
FROM
t AS tr LEFT JOIN
t AS te ON
tr.ReconcileId = te.EntryId
ORDER BY
tr.Annual_Quarterly,
tr.CurrentDate;

Answer 2

Your question is a bit vague as far as how you're wanting to subtract these values, but this should give you some idea.
Select T1.*, T1.Value - Coalesce(T2.Value, 0) As Difference
From Table T1
Left Join Table T2 On T2.[Entry Id] = T1.[Reconcile Id]