Can update accumulate?

I need to write an UPDATE statement that adds to a field from data in
another table. Can someone help? below is sample:
UPDATE TableA
SET Total = Total + TableB.Amount
FROM TableB JOIN TableA ON TableB.EmpNo = TableA.EmpNo
WHERE TableB.PrdYr = 2005
When I do this, it does not add in the incremented Total field and I end up
with the last TableB.Amount value.
Thanks.
David>> I need to write an UPDATE statement that adds to a field from data in
Yes, but you will have to provide sufficient information for others to
understand your problem. Pl. read www.aspfaq.com/5006 and post your DDLs,
sample data & expected results
Anith|||Try this, it will keep a running total in TableA each time the query is
run. If this is going to be run and needs all of the values to start
out 0 (no running total), then remove the 'Total + ' part of the query.
UPDATE TableA
SET Total = Total +
( SELECT ISNULL(SUM(TableB.Amount),0)
FROM TableB
WHERE TableB.PrdYr = 2005
and TableB.EmpNo = TableA.EmpNo
)
Kalvin|||David,
An UPDATE statement will only make one assignment
to each column. UPDATE .. FROM is a T-SQL extension
to standard SQL that allows poorly defined statements, and
while it can be handy, it can also cause confusion. I wish an
error were raised in situations like this, but that's not the case.
To do what you want, you probably need something like
update TableA set
Total = Total + (
select sum(TableB.Amount)
from TableB
where TableB.EmpNo = TableA.EmpNo
and TableB.PrdYr = 2005
)
Steve Kass
Drew University
David wrote:

>I need to write an UPDATE statement that adds to a field from data in
>another table. Can someone help? below is sample:
>UPDATE TableA
>SET Total = Total + TableB.Amount
>FROM TableB JOIN TableA ON TableB.EmpNo = TableA.EmpNo
>WHERE TableB.PrdYr = 2005
>When I do this, it does not add in the incremented Total field and I end up
>with the last TableB.Amount value.
>Thanks.
>David
>
>|||Kalvin caught one thing I didn't. This needs either COALESCE
or a WHERE condition on the update, to avoid NULLing out
Total values when there's no match in TableB. Here's a WHERE
condition that ought to do it.
update TableA set
Total = Total + (
..
)
where exists (
select *
from TableB
where TableB.EmpNo = TableA.EmpNo
and TableB.PrdYr = 2005
and TableB.Amount is not null
)
SK
Steve Kass wrote:
> David,
> An UPDATE statement will only make one assignment
> to each column. UPDATE .. FROM is a T-SQL extension
> to standard SQL that allows poorly defined statements, and
> while it can be handy, it can also cause confusion. I wish an
> error were raised in situations like this, but that's not the case.
> To do what you want, you probably need something like
> update TableA set
> Total = Total + (
> select sum(TableB.Amount)
> from TableB
> where TableB.EmpNo = TableA.EmpNo
> and TableB.PrdYr = 2005
> )
>
> Steve Kass
> Drew University
> David wrote:
>|||1) Please post DDL, so that people do not have to guess what the keys,
constraints, Declarative Referential Integrity, data types, etc. in
your schema are. Sample data is also a good idea, along with clear
specifications.
2) Would you like to learn REAL SQL or only some proprietary kludges
that have unpredicatable results, as you have posted?
Did you actually split out a year as a temporal column'!! Surely not
!
Why don't you know that column and field are **totally** different?
Why don't you know that there is no such thing as a generic, magical
"amount" -- it has to be the amount of something. Have you ever had a
BASIC -- repeat BASIC in capital letters -- data modeling class?
You can probably get enough kludges in a newsgroup to slip past your
boss unitl you get to the next job to screw up them too.
I got an email tonight form a kid who volunteered to do a DB for an
African Relief agency and seriously screwed it up. I got the consult
after things got messed up and I posted this in some newsgroups as an
example. I guess he found me via those postings.
I know his design crippled some children; I am not sure about causing
deaths and a part of me does not want to know. Please care enough not
to do that. To other people. To other people.sql