How to use FOREACH to query multiple times using the values in an aray - postgresql

Question

I want to run a query and get the rows by iterating over an array using FOREACH loop in postgresql.
I have tried using the FOREACH loop as explained in the docs but it returns an error "cannot use RETURN QUERY in a non-SETOF function"
DO
$do$
DECLARE
a integer[] := array[1,2,3];
i integer;
begin
foreach i IN ARRAY a
LOOP
RETURN QUERY
select
models.sku,
(sum(models.unitretailprice) * sum(coefficients.unit_retail_price)) +
(sum(models.flag::int) * sum(coefficients.flag::int)) +
(sum(models.mc_baseline) * sum(coefficients.mc_baseline)) +
(sum(models.mc_day_avg) * sum(coefficients.mc_day_avg)) +
(sum(models.mc_day_normal) * sum(coefficients.mc_day_normal)) +
(sum(models.mc_week_avg) * sum(coefficients.mc_week_avg)) +
(sum(models.mc_week_normal) * sum(coefficients.mc_week_normal)) +
(sum(models.sku_day_avg) * sum(coefficients.sku_day_avg)) +
(sum(models.sku_month_avg) * sum(coefficients.sku_month_avg)) +
(sum(models.sku_month_normal)* sum(coefficients.sku_month_normal)) +
(sum(models.sku_moving_avg) * sum(coefficients.sku_moving_avg)) +
(sum(models.sku_week_avg) * sum(coefficients.sku_week_avg)) +
(sum(models.sku_week_normal)* sum(coefficients.sku_week_normal)) as baseline,
(i * sum(coefficients.f)) +
(5 * sum(coefficients.p)) +
(0 * sum(coefficients.a)) as promoIncremental,
(sum(models.basket_dollar_off) * sum(coefficients.basket_dollar_off)) +
(sum(models.basket_per_off) * sum(coefficients.basket_per_off)) +
(sum(models.category_dollar_off) * sum(coefficients.category_dollar_off)) +
(sum(models.category_per_off) * sum(coefficients.category_per_off)) +
(sum(models.disc_per) * sum(coefficients.disc_per)) as couponIncremnetal
from
models join coefficients
on
models.sku = coefficients.sku
and
models.si_type = coefficients.si_type
and
models.model_type = coefficients.model_type
where
coefficients.sku in ('12841276', '11873916') and coefficients.shop_descr = 'Papercrafting Technology'
group by models.sku ;
END LOOP;
end
$do$

Answer 1

You can cross join a CTE with the factors to a derived table that is made of your current table.
WITH a (i)
AS
(
VALUES (1),
(2),
(3)
)
SELECT ...
a.i * x.sum_f + 5 * x.sum_p promoincremental,
...
FROM a
CROSS JOIN (SELECT ...
sum(coefficients.f) sum_f,
sum(coefficients.p) sum_p,
...
FROM ...) x;