Question

I have a sql database that querys the histroy data of engines. One of the features is that on a daily basis a stored procedure will search through all the data for a specific event and if the event is found it will insert it into a new table.

The problem is that this data must be unique…

The Table headers are as below:

ID / ID_Location / IDDown / IDUp / DtDown / DtUp / TimeDifference / IsExempt / Reason / Details / OrigDtUp

And the sql query is:

insert into exempts(ID_Location, iddown, idup, dtdown, dtup, timedifference)
select ID_Location, iddown, idup, dtdown, dtup, DATEDIFF(MINUTE, dtdown, dtup) as timedifference
from @tmptbl
except
select ID_Location, iddown, idup, dtdown, dtup, timedifference from exempts

But I need the query to check both the DtUp and OrigDtUp columns and ignore the timedifference as the user can change the DtUp to any value in a list and the origional DtUp value moves to OrigDtUp therfore the record is now different and the records is reinserted but with the original values??

Thanks in advance!!
Neil

Answer 1

Use a left join, it’s easier to see the logic:

   insert into exempts(ID_Location, iddown, idup, dtdown, dtup, timedifference) 
    select t.ID_Location, t.iddown, t.idup, t.dtdown, t.dtup, DATEDIFF(MINUTE, dtdown, dtup) as timedifference 
    from @tmptbl as t
      left join exempts as e 
        on  t.ID_Location = e.ID_Location 
        and t.iddown = e.iddown
        and t.idup = e.idup
        and t.dtdown = e. dtdown
        and t.DtUp = e.OrigDtUp --  <<  Match diff columns here
    where t.ID_Location is null