OT One for the msSQL experts - getting the database to do the work

Question

I need a little advice on how to use either a function or
stored procedure
to handle some update work.
Basically I am building an application where customers are
assigned points
values based on the products that they have bought. In the
Orders table a
value is assigned to each order and I can get the total
points per customer
by running the following Select statement
SELECT Cust_ID, SUM(Order_Points) as PointsTotal
FROM tblOrders
WHERE Status_ID in (3,5,6)
GROUP BY Cust_ID
What I then want to do is the take the number for each
Customer and update
the value in a field called Cust_Points in tblCustomers.
I could simple write this to a dataset on the page, loop
through it and run
an update statement for each customer, but given that I am
using msSQL I am
sure that there is some way to write this whole action inside
of a stored
procedure or function and then just call that to handle the
work.
I am using ASP.Net C# for the pages.
Any help gratefully received.
Paul Whitham
Certified Dreamweaver MX2004 Professional
Adobe Community Expert - Dreamweaver
Valleybiz Internet Design
www.valleybiz.net

Answer 1

"Paul Whitham AdobeCommunityExpert"
<[email protected]> wrote in message
news:es8q3e$rle$[email protected]..
> I could simple write this to a dataset on the page, loop
through it and
> run an update statement for each customer, but given
that I am using msSQL
> I am sure that there is some way to write this whole
action inside of a
> stored procedure or function and then just call that to
handle the work.
Good instinct. :)
What you need in this case is a trigger.
You'll need to add an INSERT and/or UPDATE trigger to your
tblOrders table.
Which one you need (or if you need both) depends on your
workflow. I notice
you're only counting orders with certain status values. If an
order can be
inserted with one of those values, then you need an INSERT
trigger. If an
order gets one of those values on a later update, you need an
UPDATE
trigger. If either could be the case, you need both.
Your basic outline is:
INSERT trigger: if status is in (3,5,6) then add points to
tblCustomer.
UPDATE trigger: if status has changed from something other
than (3,5,6) and
is in (3,5,6), then add points to tblCustomer. If status has
changed from
something in (3,5,6) to something NOT in (3,5,6), then
subtract points from
tblCustomer. If status has not changed or does not change
"groups" (for
instance, was 3 becomes 5 or was 0 becomes 2), then do
nothing.
Here's some good resources on the basics of triggers in SQL
Server. These
should get you the knowledge you need. If you've got specific
questions
about the trigger afterward, then I'd suggest opening a new
thread just so
this one doesn't fall off.
Basics:
http://www.aspfree.com/c/a/MS-SQL-Server/Triggers/
That should be all you need this time around. Here's the rest
just for
completeness' sake:
Specifics:
http://www.aspfree.com/c/a/MS-SQL-Server/Trigger-Specifics/
Managing:
http://www.aspfree.com/c/a/MS-SQL-Server/Trigger-Management/