Query using link server to an Oracle database failswhile similar query works

Question

I have two queries almost the same that use a link to an Oracle database. One works ok, the other is a copy of the first with a few fields selects removed.  The first one works fine, the copy fails with: Cannot get the data of the row from the OLE DB
provider "OraOLEDB.Oracle" for linked server "linkname".
They are so similar, why would one work but not the other? 
First query, this one works:
SET
ANSI_NULLS ON
GO
SET
QUOTED_IDENTIFIER ON
GO
CREATE
PROCEDURE [dbo].[procedure_name]
-- Add the parameters for the stored procedure here
@Begindate  Datetime,
@Enddate Datetime
AS
BEGIN
--SET NOCOUNT ON added to prevent extra result sets from
--interfering with SELECT statements.
SET NOCOUNT
ON;
-- Insert statements for procedure here
select p.patientid, p.testid,
mdx."Dx_4", td.acquisitiondatetime_dt, td.democompletedatetime_dt,
td.editdatetime_dt,
CAST(STUFF(STUFF(mn."Arrival_Time_9",
9, 0,
' '), 12, 0,
AS datetime)
as Arrival_date,
CAST(STUFF(STUFF(mt."Comp_D_T_22",
9, 0,
' '), 12, 0,
AS datetime)
as Order_date, td.confirmdatetime_dt
(CAST(DATEDIFF
(MINUTE,
CAST (STUFF
(STUFF
(MN."ARRIVAL_TIME_9", 9,0,
' '), 12, 0,
AS DATETIME), TD.DEMOCOMPLETEDATETIME_DT) 
as char(10))
+ 'min')
AS "ARRIVAL TO COMPLETE",
(CAST(DATEDIFF
(MINUTE,
CAST (STUFF
(STUFF
(MT."COMP_D_T_22", 9,0,
' '), 12, 0,
AS DATETIME), TD.DEMOCOMPLETEDATETIME_DT)
as char(10))
+ 'min') 
AS "ORDER TO COMPLETE"
from linknametosqldb.sqldbname.dbo.tstpatientdemographics
as p inner
join linknametosqldb.sqldbname dbo.tsttestdemographics
as td on p.testid
= td.testid
left
outer join linknametooracledb."M01Tab01_Main" mn
on td.visitnumber
= mn."Pt_Acct_5"
inner
JOIN linknametooracledb."M01Tab06_Ord" mt
ON mn."Master_Recid_1"
= mt."Master_Recid_1"
inner
join linknametooracledb."M01Tab09_Dx" mdx
on mn."Master_Recid_1"
= mdx."Master_Recid_1"
where td.location
in (2, 4)
and mt.order_4
like 'EKG%' 
and mdx."Dx_4"
like '%Chest Pain%'
and
(td.acquisitiondatetime_dt
>= @Begindate and td.acquisitiondatetime_dt
< @Enddate)
order
by p.patientfullname_last, p.patientfullname_first
END
GO
Second query, copied from first with some fields selects removed, this does not work:
SET
ANSI_NULLS ON
GO
SET
QUOTED_IDENTIFIER ON
GO
CREATE
PROCEDURE [dbo].[procedure_name_2]
-- Add the parameters for the stored procedure here
@Begindate  Datetime,
@Enddate Datetime
AS
BEGIN
--SET NOCOUNT ON added to prevent extra result sets from
--interfering with SELECT statements.
SET NOCOUNT
ON;
-- Insert statements for procedure here
select p.patientid, mdx."Dx_4",
td.democompletedatetime_dt,
CAST(STUFF(STUFF(mn."Arrival_Time_9",
9, 0,
' '), 12, 0,
AS datetime)
as EDIS_Arrival_date,
(CAST(DATEDIFF
(MINUTE,
CAST (STUFF
(STUFF
(MN."Arrival_Time_9", 9,0,
' '), 12, 0,
AS DATETIME), TD.DEMOCOMPLETEDATETIME_DT) 
as char(10))
+ 'min')
AS "ARRIVAL TO COMPLETE"
from linknametosqldb.dbo.tstpatientdemographics
as p inner
join linknametosqldb.dbo.tsttestdemographics
as td on p.testid
= td.testid
left outer
join linknametooracledb."M01Tab01_Main" mn
on td.visitnumber
= mn."Pt_Acct_5"
inner
JOIN linknametooracledb."M01Tab06_Ord" mt
ON mn."Master_Recid_1"
= mt."Master_Recid_1"
inner
join linknametooracledb M01Tab09_Dx" mdx
on mn."Master_Recid_1"
= mdx."Master_Recid_1"
where td.location
in (2, 4)
and mt.order_4
like 'EKG%' 
and mdx."Dx_4"
like '%Chest Pain%'
and
(td.acquisitiondatetime_dt
>= @Begindate and td.acquisitiondatetime_dt
< @Enddate)
order
by p.patientid
END
GO
Thanks very much for any help with this.

Answer 1

* Consider putting parentheses around the 3 oracle tables so the 3 of them can possibly be treated as a unit.  Assuming there's some performance impact due to the linked server, this MIGHT help, may do a little joining over on the Oracle side of
the world.  In either case, it's a little cleaner.  They syntax below, including a few extra line breaks for clarity, should be correct.  (try the change to the ON clause suggested above too, though).
The parentheses will not help much. SQL Server will remote (as the term is) the query to the Oracle instance if this appears to have a lower cost and there is nothing the blocks remoting.
On the other hand, OPENQUERY can be an alternative to ensure that this happens:
 left outer join
    OPENQUERY (linknametooracledb,
               'SELECT ...
                FROM   "M01Tab01_Main" mn
                JOIN   "M01Tab06_Ord" mt ON mn."Master_Recid_1" = mt."Master_Recid_1"
                JOIN   "M01Tab09_Dx" mdx on mn."Master_Recid_1" = mdx."Master_Recid_1"') mn on td.visitnumber = mn."Pt_Acct_5"
But this presumes that you there are no columns from the SQL Server side that are used to select data from the Oracle side. That is, the above could lead to far much data being brought across the wire.
Then again, this does not really seem to relate to the original problem where a stored procedure was not working at all. That problem is not very easy to assist with since code post is the not the authentic code as pointed out in the thread. For instance
inner JOIN linknametooracledb."M01Tab06_Ord"
Has nothing to do with Oracle, but accesses a table in the schema linknametooracledb.
I think to help dmcm, you need a really good crystal ball - at least as long he/she does not share the actual code.
Erland Sommarskog, SQL Server MVP, [email protected]