Mark Walker wrote: > I'm not sure what you're trying to do but, it appears that you database > design is incorrect. What you need is something like > > CREATE TABLE temp_readings > ( > _date Date, > temperature double, > source varchar(20), > ) > > No reading, no record. Are you suggesting that you would have a weekly > set of records for each row? > > CREATE TABLE temp_readings > ( > weekstart date, > sun double, > mon double, > tues, double > etc > ) > > Not such a great way to do it. Ummm, I'm not trying to make a temperature database. I was responding to the previous poster with an extremely simple example of usefulness of the _concept_ of "null". I'm afraid I hadn't considered the possibility that it would be mistaken as an example of an actual table. But since you bring it up, simply omitting rows isn't necessarily an option. A common scenario for weather observation is to take regular snapshots or a bunch of measurements (air-temperature, humidity, wind-speed, soil-temperature, leaf-wetness, UV radiation, etc.) which can easily be represented in a table with a timestamp and a column for each of the measurements. In a modular weather station where a specific instrument can be out of service, one or more of those measurements could be missing (null) for a period of time while the remaining measurements are still being inserted. Cheers, Steve
