Re: filtering based on table of start/end times

On 11/7/2014 3:12 PM, Seb wrote:
> Hi,
>
> At first glance, this seemed simple to implement, but this is giving me
> a bit of a headache.
>
> Say we have a table as follows:
>
> CREATE TABLE voltage_series
> (
> voltage_record_id integer NOT NULL DEFAULT nextval('voltage_series_logger_record_id_seq'::regclass),
> "time" timestamp without time zone NOT NULL,
> voltage numeric,
> CONSTRAINT voltage_series_pkey PRIMARY KEY (voltage_record_id));
>
> So it contains a time series of voltage measurements. Now suppose we
> have another table of start/end times that we'd like to use to filter
> out (or keep) records in voltage_series:
>
> CREATE TABLE voltage_log
> (
> record_id integer NOT NULL DEFAULT nextval('voltage_log_record_id_seq'::regclass),
> time_beg timestamp without time zone NOT NULL,
> time_end timestamp without time zone NOT NULL,
> CONSTRAINT voltage_log_pkey PRIMARY KEY (record_id));
>
> where each record represents start/end times where the voltage
> measurement should be removed/kept. The goal is to retrieve the records
> in voltage_series that are not included in any of the periods defined by
> the start/end times in voltage_log.
>
> I've looked at the OVERLAPS operator, but it's not evident to me whether
> that is the best approach. Any tips would be appreciated.
>
> Cheers,
>

Hello Seb,

Any reason this won't work for you?

SELECT *
FROM voltage_series
WHERE time NOT IN (SELECT DISTINCT time FROM voltage_series,
voltage_log WHERE time BETWEEN time_beg AND time_end);

Might not be the fastest way to do it, if the tables are large.
Apologies if I've not understood your question properly.

Regards,
Bryan

--
______________
Postdoctoral Researcher
GA Cooperative Fish & Wildlife Research Unit
Warnell School of Forestry & Natural Resources
University of Georgia
Athens 30602-2152