SQL Update Where Exists If Then Else

I am trying to update contents of a field in a table based on the results of a subquery.  I have been able to get the statement to work for an individual row, but I cannot figure out the syntax to run this update against all the rows in the table.

Basically the query looks to see if there was activity in another table for a given year and month and if sees activity update the base table with that count, and if it finds no activity it should update the field with a zero (0)

******** Single part version THIS WORKS BUT I NEED IT TO RUN AGAINS ALL PARTS IN THE BASE TABLE*********

If(EXISTS
(
select UnitsSold
from
(SELECT  partno,warehouse,YEAR(EntryDate) AS 'WOYear', MONTH(EntryDate) AS 'WOMonth', SUM(qty) AS 'UnitsSold',
count(wono) as "Workorders"
FROM woparts
GROUP BY partno,warehouse,YEAR(EntryDate), MONTH(EntryDate)
) C
where C.partno = '0040596'
and C.warehouse = 'inactive'
and C.WOMonth = month(dateadd(m,-3,getdate()))
and C.WOYear = year(dateadd(m,-3,getdate()))
))
      BEGIN
        UPDATE ab_partsdemand
            set demand4=
                  (
                  select UnitsSold
                  from
                  (SELECT  partno,warehouse,YEAR(EntryDate) AS 'WOYear', MONTH(EntryDate) AS 'WOMonth', SUM(qty) AS 'UnitsSold',
                  count(wono) as "Workorders"
                  FROM woparts
                  GROUP BY partno,warehouse,YEAR(EntryDate), MONTH(EntryDate)
                  ) C
                  where C.partno = '0040596'
                  and C.warehouse = 'inactive'
                  and C.WOMonth = month(dateadd(m,-3,getdate()))
                  and C.WOYear = year(dateadd(m,-3,getdate()))
                  )
                  where partno = '0040596'
                  and warehouse = 'inactive'
      END
else
        UPDATE ab_partsdemand
            set demand4=0
            where partno = '0040596'
            and warehouse = 'inactive'
josephpmoCFOAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

gplanaCommented:
this subquery:
(
                  select UnitsSold
                  from
                  (SELECT  partno,warehouse,YEAR(EntryDate) AS 'WOYear', MONTH(EntryDate) AS 'WOMonth', SUM(qty) AS 'UnitsSold',
                  count(wono) as "Workorders"
                  FROM woparts
                  GROUP BY partno,warehouse,YEAR(EntryDate), MONTH(EntryDate)
                  ) C
                  where C.partno = '0040596'
                  and C.warehouse = 'inactive'
                  and C.WOMonth = month(dateadd(m,-3,getdate()))
                  and C.WOYear = year(dateadd(m,-3,getdate()))
)

has to return a single value. So my question is: what to do if it returns 2 or more values ? I figure the result you want in that case is the SUM, so put this:

       UPDATE ab_partsdemand
            set demand4=
                  (
                  select SUM(UnitsSold ) -- <<<<<<<<<<<<<<<<  This is the only line I changed
                  from
                  (SELECT  partno,warehouse,YEAR(EntryDate) AS 'WOYear', MONTH(EntryDate) AS 'WOMonth', SUM(qty) AS 'UnitsSold',
                  count(wono) as "Workorders"
                  FROM woparts
                  GROUP BY partno,warehouse,YEAR(EntryDate), MONTH(EntryDate)
                  ) C
                  where C.partno = '0040596'
                  and C.warehouse = 'inactive'
                  and C.WOMonth = month(dateadd(m,-3,getdate()))
                  and C.WOYear = year(dateadd(m,-3,getdate()))
                  )
                  where partno = '0040596'
                  and warehouse = 'inactive'

0
cyberkiwiCommented:
You should optimize the YEAR(EntryDate) and Month(Entry) expressions to use the index by working out the date range, but if the partno+warehouse is selective enough, it is probably not an issue.
        UPDATE ab_partsdemand
            set demand4=
                  ISNULL((
                  (SELECT  SUM(qty)
                  FROM woparts
                  WHERE woparts.partno = ab_partsdemand.partno
                  AND woparts.warehouse = 'inactive'
                  AND YEAR(EntryDate) = year(dateadd(m,-3,getdate()))
                  AND MONTH(EntryDate) = month(dateadd(m,-3,getdate()))
                  ),0)
                  where warehouse = 'inactive'

Open in new window

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
josephpmoCFOAuthor Commented:
CyberKiwi,

Thanks a very elegant solution.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft SQL Server

From novice to tech pro — start learning today.