Question

I’m trying to select most recent date from one table (invoice) to a customer on another table. I’m not looking for a single customer, but several. What I want to do looks something like this:

select C.[Last Name], C.[First Name], C.[State], I.[Date]  
From myDb.dbo.Customer C  
left join myDb.dbo.Invoice I on I.CustomerID = C.CustomerID  
where c.state=@State and i.date = max(i.date)

I know I can’t have the Max() in the where, and I tried using HAVING. I can’t assign a local var for the customerID and do a where i.date = (select...). I’m trying to keep this all as one statement as this is being executed on several DB’s from a single DB.

update:
I’ve decided to change my design requirements as this wasn’t the most optimal solution.

Answer 1

You possibly want to group:

select C.[Last Name], C.[First Name], C.[State], max(I.[Date]) as [Date]
from myDb.dbo.Customer C
    left join myDb.dbo.Invoice I on I.CustomerID = C.CustomerID
where C.state = @State
group by C.[Last Name], C.[First Name], C.[State]

Updated:

select A.[Last Name], A.[First Name], A.[State], B.[Date]
from myDb.dbo.Customer A
    join (
        -- Get Customers by State with their most recent Invoice Date
        select C.[CustomerID], max(I.[Date]) as [Date]
        from myDb.dbo.Customer C
            left join myDb.dbo.Invoice I on I.[CustomerID] = C.[CustomerID]
        where C.[State] = @State
        group by C.[CustomerID]
    ) B on A.[CustomerID] = B.[CustomerID]