Question

select  first(orderid), accountid 
from [Order] 
group by AccountId 
order by DateCreated desc

first() is invalid function.

max() does not work for unique identifiers

How would I get the last orderid created for all accounts? Thanks.

Answer 1

Something like (untested):

;WITH CTE_LatestOrders AS (
    select accountid, lastcreated = max(datecreated)
    from [Order]
    group by accountid
)
select
    accountid, orderid
from
    [Orders] o
    join CTE_LatestOrders l 
        on o.AccountID = l.AccountID 
        and o.datecreated = l.lastcreated