Question

Below you can see my simplified DB model:

Due to an error there are only null-values in the column Job.location where the entries belong to a certain Plan. Therefore I want to update all Jobs associated with this Plan, setting Job.location to Location.name of the User, who owns this Plan.

I tried this SQL query:

    update dbo.Job set location =

        (select name from dbo.Location as loc where

           loc.objectid = objectid  and loc.user_id in 

           (select userid from dbo.[Plan] as p where p.planid = 20))

        where planid = 20

However, the result is always: 0 rows affected. The subqueries itself work correctly.

How can I achieve that all Jobs with a certain planid are affected?

Answer 1

I think you mistake may be that you have no alias for objectid column in subquery loc.objectid = objectid, so when you running subquery by itself, it just works like loc.objectid = loc.objectid and when you running it in the update, it works like loc.objectid = dbo.Job.objectid

In your schema it’s possible to have multiple locations for users, but supposing you have only one location per user and object, you can try this query:

update dbo.Job set
    location = L.Name
from dbo.Job as J
    inner join dbo.[Plan] as P on P.planid = J.planid
    inner join dbo.Location as L on L.user_id = P.userid and L.objectid = J.objectid