SQL Inner join not working to get change from previous date - sql

Question

I have a table with the following data :
TradeDate Stock BuySell DayClose
--------------------------------------
10-Dec-12 ABC 1 11
10-Dec-12 ABC 2 12
11-Dec-12 ABC 1 11.5
11-Dec-12 ABC 2 12.5
11-Dec-12 DEF 1 15
11-Dec-12 DEF 2 16
and I want to query on it for a particular date 11-Dec-2012 to get the following output :
Stock Buy Sell Mid Change
--------------------------------------
ABC 11.5 12.5 12.0 0.5
DEF 15 16 15.5
Since DEF does not have data for the previous date, change should be blank for it.
I have created the following query :
Select Stock,
AVG(CASE BuySell WHEN 1 THEN DayClose END) AS 'Buy',
AVG(CASE BuySell WHEN 2 THEN DayClose END) As 'Sell',
Sum(DayClose/2) as 'Mid',
Sum(Change/2) AS Change
FROM (
select t1.Stock, t1.BuySell, t1.DayClose, Sum(t1.DayClose - t2.DayClose) as Change
FROM #myTable as t1 inner join #myTable as t2 on
t1.Stock = t2.Stock
where
t1.TradeDate = '2012-12-11' AND
t2.TradeDate = (SELECT TOP 1 TradeDate FROM #myTable WHERE TradeDate < '2012-12-11' ORDER BY TradeDate DESC)
GROUP BY
t1.Stock, t1.buysell, t1.dayclose ) AS P1 GROUP BY stock
I created a temp table #mytable for this purpose :
drop table #mytable
CREATE TABLE #myTable
(
TradeDate datetime,
stock varchar(20),
buysell int,
dayclose decimal(10,2)
)
insert into #mytable values ('10-dec-2012', 'abc' , 1, 11)
insert into #mytable values ('10-dec-2012', 'abc' , 2, 12)
insert into #mytable values ('11-dec-2012', 'abc' , 1, 11.5)
insert into #mytable values ('11-dec-2012', 'abc' , 2, 12.5)
insert into #mytable values ('11-dec-2012', 'def' , 1, 15)
insert into #mytable values ('11-dec-2012', 'def' , 2, 16)
But I am not able to get the required output, rather getting
Stock Buy Sell Mid Change
--------------------------------------------------------------
abc 11.500000 12.500000 12.00000 1.00
Can someone tell me where am I going wrong. I seem to be lost in here.
Thanks,
Monika

Answer 1

Please try:
;WITH T1 as(
SELECT a.TradeDate
,a.stock
,SUM(CASE WHEN a.BuySell = 1 THEN a.DayClose ELSE 0 END) Buy
,SUM(CASE WHEN a.BuySell = 2 THEN a.DayClose ELSE 0 END) Sell
,SUM(a.DayClose) / 2 AS Mid
FROM #mytable a
GROUP BY a.TradeDate, a.stock
)SELECT t.*,
t.Mid - PR.Mid AS Change
FROM T1 t
LEFT JOIN
T1 PR ON
PR.TradeDate = DATEADD(DAY, -1, t.TradeDate)
AND PR.stock = t.stock

Answer 2

Try this:
SELECT a.TradeDate
,a.stock
,SUM(CASE WHEN a.BuySell = 1 THEN a.DayClose ELSE 0 END) Buy
,SUM(CASE WHEN a.BuySell = 2 THEN a.DayClose ELSE 0 END) Sell
,SUM(a.DayClose) / 2 AS Mid
INTO #temp
FROM #mytable a
GROUP BY a.TradeDate, a.stock
SELECT t.*,
t.Mid - previousRecord.Mid AS Change
FROM #temp t
LEFT JOIN
#temp previousRecord ON
previousRecord.TradeDate = DATEADD(DAY, -1, t.TradeDate)
AND previousRecord.stock = t.stock
DROP TABLE #temp
All you have to do now is to select the data for a date.

Answer 3

Select Stock,
AVG(CASE BuySell WHEN 1 THEN DayClose END) AS 'Buy',
AVG(CASE BuySell WHEN 2 THEN DayClose END) As 'Sell',
Sum(DayClose/2) as 'Mid',
Sum(Change/2) AS Change
FROM (
select t1.Stock, t1.BuySell, t1.DayClose, Sum( t1.DayClose - t2.DayClose ) as Change
FROM #myTable as t1 left join #myTable as t2 on t2.TradeDate = (SELECT TOP 1 TradeDate FROM #myTable WHERE TradeDate < t1.TradeDate ORDER BY TradeDate DESC)
and t1.Stock = t2.Stock and t1.buysell=t2.buysell
where
t1.TradeDate = '11-12-2012'