SQL Server LEFT JOIN - sql-server

Question

This query has been keeping me busy for the last couple of days. I tried to rewrite it with different ideas but I keep having the same problem. To simplify the problem I put part of my query in a view, this view returns 23 records. Using a left join I would like to add fields coming from the table tblDatPositionsCalc to these 23 records. As you can see I have an additional condition on the tblDatPositionsCalc in order to only consider the most recent records. With this condition it would return 21 records. The join should be on two fields together colAccount and colId.
I simply want the query to return the 23 records from the view and where possible have the information from tblDatPositionsCalc. There is actually only 2 records in the view without corresponding id and account in tblDatPositionsCalc, that means out of the 23 records only 2 will have missing values in the fields coming from the table tblDatPositionsCalc.
The problem with my query is that it only returns the 21 records from tblDatPositionsCalc. I don't understand why. I tried to move the condition on date in just after the JOIN condition but that did not help.
SELECT TOP (100) PERCENT
dbo.vwCurrPos.Account,
dbo.vwCurrPos.Id,
dbo.vwCurrPos.TickerBB,
dbo.vwCurrPos.colEquityCode,
dbo.vwCurrPos.colType,
dbo.vwCurrPos.colCcy,
dbo.vwCurrPos.colRegion,
dbo.vwCurrPos.colExchange,
dbo.vwCurrPos.[Instr Type],
dbo.vwCurrPos.colMinLastDay,
dbo.vwCurrPos.colTimeShift,
dbo.vwCurrPos.Strike,
dbo.vwCurrPos.colMultiplier,
dbo.vwCurrPos.colBetaVol,
dbo.vwCurrPos.colBetaEq,
dbo.vwCurrPos.colBetaFloor,
dbo.vwCurrPos.colBetaCurv,
dbo.vwCurrPos.colUndlVol,
dbo.vwCurrPos.colUndlEq,
dbo.vwCurrPos.colUndlFut,
tblDatPositionsCalc_1.colLots,
dbo.vwCurrPos.[Open Positions],
dbo.vwCurrPos.colListMatShift,
dbo.vwCurrPos.colStartTime,
tblDatPositionsCalc_1.colPrice,
tblDatPositionsCalc_1.colMktPrice,
dbo.vwCurrPos.colProduct,
dbo.vwCurrPos.colCalendar,
CAST(dbo.vwCurrPos.colExpiry AS DATETIME) AS colExpiry,
dbo.vwCurrPos.colEndTime,
CAST(tblDatPositionsCalc_1.colDate AS datetime) AS colDate,
dbo.vwCurrPos.colFund,
dbo.vwCurrPos.colExchangeTT,
dbo.vwCurrPos.colUserTag
FROM dbo.vwCurrPos
LEFT OUTER JOIN dbo.tblDatPositionsCalc AS tblDatPositionsCalc_1
ON tblDatPositionsCalc_1.colId = dbo.vwCurrPos.Id
AND tblDatPositionsCalc_1.colAccount = dbo.vwCurrPos.Account
WHERE (tblDatPositionsCalc_1.colDate =
(SELECT MAX(colDate) AS Expr1 FROM dbo.tblDatPositionsCalc))
ORDER BY
dbo.vwCurrPos.Account,
dbo.vwCurrPos.Id,
dbo.vwCurrPos.colEquityCode,
dbo.vwCurrPos.colRegion
Any idea what might cause the problem?

Answer 1

(Option 1) DrCopyPaste is right so your from clause would look like:
...
FROM dbo.vwCurrPos
LEFT OUTER JOIN dbo.tblDatPositionsCalc AS tblDatPositionsCalc_1
ON tblDatPositionsCalc_1.colId = dbo.vwCurrPos.Id
AND tblDatPositionsCalc_1.colAccount = dbo.vwCurrPos.Account
and (tblDatPositionsCalc_1.colDate =
(SELECT MAX(colDate) AS Expr1 FROM dbo.tblDatPositionsCalc))
...
reason: the where clause restriction of left joined to column = some expression with fail to return for "null = something" so the row will be removed.
(Option 2) As oppose to pushing code in to additional views where it is harder to maintain you can nest sql select statements;
select
X.x1,X.x2,
Y.*
from X
left join
(select Z.z1 as y1, Z.z2 as y2, Z.z3 as y3
from Z
where Z.z1 = (select max(Z.z1) from Z)
) as Y
on x.x1 = Y.y1 and X.x2 = Y.y2
The advantage here is you check each nested sub query a move out quickly. Although if you still building up more logic check out common table expressions (CTE's) http://msdn.microsoft.com/en-us/library/ms175972.aspx