Working with Trigger in Postgresql and QGIS Part II

#qgis #postgresql #surveykshak
How to work with Triggers in Postgresql and QGIS Part II.
In this video we have added two triggers : How to update length in meter and kilometer in their respective field.

The command we have run in videos are as below:
--Add column
ALTER TABLE roads ADD COLUMN length_km double precision;

--Create trigger function
CREATE OR REPLACE FUNCTION length_m_trigger_function() RETURNS trigger AS $$
BEGIN
NEW.length_m=(st_length(NEW.geom))::decimal(10,2);
RETURN NEW;
END;
$$ language plpgsql;

--Apply trigger to table
CREATE TRIGGER length_m_trigger
BEFORE INSERT OR UPDATE
ON roads
FOR EACH ROW
EXECUTE PROCEDURE length_m_trigger_function();

--Projection transformation of layer

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DISCLAIMER

The Information provided on, from or through this channel is general in nature and is solely for educational purposes.
00:00 Introduction
01:25 Length trigger
09:00 Projection transformation