On 10/13/2011 08:31 AM, Raymond O'Donnell wrote:
Hi Ray,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. 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 --
Stephen Clark NetWolves Sr. Software Engineer III Phone: 813-579-3200 Fax: 813-882-0209 Email: steve.clark@xxxxxxxxxxxxx http://www.netwolves.com |
