Write a trigger function to update column value based on another column value within same table in postgresql

Question

I have a table called 'tbl_abcd' with columns 'id, user_id', 'carbon_value', 'total_carbon' and 'area'in which id is the primary key.I want to write a trigger function when user update any change in 'carbon_value' column and that trigger will invoke a function that should update 'total_carbon' column value that will be calculated by the formula 'area*carbon_value' for which total_carbon will be changed.

for example carbon_value = 3, area = 5hectare, total_carbon = 3*5 = 15. when carbon value will changed automatically total carbon will be changed.

Any help will be highly appreciated. Rutuparna Panda

Kouber Saparev · Accepted Answer · 2021-01-05 12:09:14Z

3

CREATE FUNCTION total_carbon() RETURNS trigger AS $$
  BEGIN
    NEW.total_carbon := NEW.carbon_value * NEW.area;

    RETURN NEW;
  END
$$ LANGUAGE plpgsql;


CREATE TRIGGER
  total_carbon
BEFORE INSERT OR UPDATE ON
  tbl_abcd
FOR EACH ROW EXECUTE PROCEDURE
  total_carbon();

answered Jan 5, 2021 at 12:09

Kouber Saparev

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