PostgreSQL:UPPDATERA med aggregatfunktion

Här är ett allmänt exempel på hur man gör det.

UPDATE public.customer_value cv
SET total_value = sub_q.sum_val 
FROM 
    (
    SELECT SUM(order_amount) AS sum_val, o.customer_id 
    FROM public.orders AS o
    GROUP BY o.customer_id
    ) AS sub_q
WHERE sub_q.customer_id = cv.customer_id;

Om du vill prova det här exemplet i sin helhet kan du skapa dummydata så här:

CREATE TABLE public.customer_value
(
  customer_id int 
, total_value numeric (10,2)
);

CREATE TABLE public.orders 
(
  customer_id int
, order_amount numeric(10,2)
);

INSERT INTO public.customer_value
(customer_id)
VALUES 
  (1)
, (2);


INSERT INTO public.orders
(customer_id, order_amount)
VALUES 
 (1, 10)
,(1, 10)
,(2, 7.5)
,(2, 7.5);