On 10/13/2011 08:31 AM, Raymond O'Donnell wrote:
On 13/10/2011 12:17, Steve Clark wrote:
Hello List,
I am a not very experienced writing sql and I have a problem I can't
readily solve, so
I was hoping to get some help from this great list.
Here is my problem I have a table that has event data about the status
of units in the field. It has
many kinds of events one of which has down time information. I have
written a query to extract that
information and calculate the % downtime. The problem I am having is
that if the unit was never down
I don't see it in my query, I would like to be able to somehow report it
as 100% up.
The way I'd approach this is to do a LEFT OUTER JOIN between the units
table and the events table, with the units on the left of the join: this
way any particular unit will always appear in the result set, and if
there are no corresponding rows in the events table then you know that
the unit had 100% uptime.
HTH.
Ray.
Hi Ray,
Thanks for the response, I am afraid I don't know enough on how to formulate the left outer join
so I have attacked the problem from a different direction. Creating a temporary table with all
the units set to 100% then running my existing query and using the results to update my
temporary table where the unit serial no's match.
Steve