Gillesie

Im having this rather complex query problem I'd like resolved. 1 table, 4 Columns, tblErrors: TramId(3) ErrorCode(1) Date (yyyy-mm-dd) Time(hh:mm:ss) 200 A 2005-01-01 12:15:01 200 A 2005-01-01 12:17:02 201 A 2005-01-01 13:00:15 201 B 2005-01-01 12:17:30 .... The key is all 4 columns together. Basically the same error can occur only once at the same time (second) on a particular tram. Say now I want the record count of everytime ErrorCode 'A' happens in a time interval of 3 minutes before ErrorCode 'B' occurs. In my example the count would be 2. record 1 and 2 happen within that time interval of 3 minutes. The reason I need this query, is to find a link between 2 errorcodes. This table contains hundreds of thousands of records though.