Thank you greatly for the FAQ link. I learned a lot just reading it.

The table:
if exists (select * from dbo.sysobjects where id =
object_id(N'[tblProfileTemp]') and OBJECTPROPERTY(id, N'IsUserTable') =
1)
drop table [tblProfileTemp]
GO

if not exists (select * from dbo.sysobjects where id =
object_id(N'[dbo].[tblProfileTemp]') and OBJECTPROPERTY(id,
N'IsUserTable') = 1)
BEGIN
CREATE TABLE [tblProfileTempX] (
--[Item] [int] IDENTITY (1, 1) NOT NULL ,
[Item] [int] NOT NULL ,
[EntryTime] [datetime] NULL ,
[RunTime] [numeric](12, 3) NULL ,
[Speed] [int] NULL ,
[gross] [int] NULL ,
[net] [int] NULL
) ON [PRIMARY]
END

The insert statements (the code to generate this was an education in
itself).
(10 rows should be enough) I commented out the identity contraint so
inserting w/o the column list would be possible.
INSERT INTO [tblProfileTempx] VALUES(1,'Jun 21 2005
9:09:13:310PM',0.000,0,0,0)
INSERT INTO [tblProfileTempx] VALUES(2,'Jun 21 2005
9:09:19:370PM',6.060,9000,NULL,NULL)
INSERT INTO [tblProfileTempx] VALUES(3,'Jun 21 2005
9:09:21:310PM',8.000,NULL,95,NULL)
INSERT INTO [tblProfileTempx] VALUES(4,'Jun 21 2005
9:10:12:380PM',59.070,9000,NULL,NULL)
INSERT INTO [tblProfileTempx] VALUES(5,'Jun 21 2005
9:10:24:310PM',71.000,NULL,253,NULL)
INSERT INTO [tblProfileTempx] VALUES(6,'Jun 21 2005
9:11:24:370PM',131.060,8000,NULL,NULL)
INSERT INTO [tblProfileTempx] VALUES(7,'Jun 21 2005
9:11:27:310PM',134.000,NULL,410,NULL)
INSERT INTO [tblProfileTempx] VALUES(8,'Jun 21 2005
9:11:51:320PM',158.010,NULL,438,NULL)
INSERT INTO [tblProfileTempx] VALUES(9,'Jun 21 2005
9:11:51:490PM',158.180,0,NULL,NULL)
INSERT INTO [tblProfileTempx] VALUES(10,'Jun 21 2005
9:13:51:310PM',278.000,NULL,446,NULL)

Explanation of data:
The data represents the output of a running press. Each data element
is recorded at EntryTime. RunTime represents the time elapsed since
the start, and is expressed in seconds. Gross is number of copies
printed. Net is number of copies not rejected automatically by various
defect detectors.


Desired Result:
Example:
Gross for item 1 is 0
Gross for item 2 is null
Gross for item 3 is 95

I need to replace the null in item 2 with a value that represents the
gross count for that time, assuming a constant press speed. It will
not necesarily be constant, but the error will be slight.

The formula for that value will be:

Gross2 = Gross1 + ((Gross3 - Gross1) * ((RunTime2-RunTime1) / (RunTime3
- RunTime1)))

Similar interpolations will be calculated for Net and Speed.

It gets harder where there are two or more nulls between known values.

I was working along the lines of:

Update t1
Set t1.Gross = t0.Gross + ((t2.Gross = t0.Gross) *
((t1.runtime-t0.runtime)/(t2.runtime-t0.runtime)))

from tblProfileTempX t1 inner join tblProfileTempX t0 on t0.item =
t1.item
inner join tblProfileTempX t2 on t2.item = t0.item

where t1.gross is null
and t0.EntryTime = (select Max(EntryTime) from tblProfileTempX
where gross is not null and item < t1.item)
and t2.EntryTime = (select Min(EntryTime) from tblProfileTempX
where gross is not null and item > t1.item)

I've reduce the errors to the following:
Server: Msg 170, Level 15, State 1, Line 2
Line 2: Incorrect syntax near '='.
Server: Msg 156, Level 15, State 1, Line 9
Incorrect syntax near the keyword 'and'.

Thanks in advance for your time and effort, and apologies for the group
etiquette breach,

Regards,
BM

David Portas wrote:
> I expect it will be possible with an UPDATE and a join/subquery.
>
> UPDATE YourTable
> SET speed =
> (SELECT ...
> FROM YourTable
> WHERE entrytime < YourTable.entrytime ...)
> WHERE speed IS NULL
>
> If you need a complete solution then explain the calculation, show the
> result you want and post DDL for the table. Also, it's best to post sample
> data as INSERT statements so that others can more easily test out possible
> solutions. That way you'll get accurate and useful answers more quickly.
> See:
> http://www.aspfaq.com/etiquette.asp?id=5006
>
> --
> David Portas
> SQL Server MVP
> --