Postgres update a diferent table - sql

Question

Hello im trying to create a trigger, after insert on a certain column on a certain row the trgigger adds the that value on the other table on a certain place.
I have a table called updates:
create table public.updates (
id serial not null,
matricula varchar(10) NOT NULL,
primensalidade int,
segmensalidade int,
tercmensalidade int,
quamensalidade int,
quimensalidade int,
sexmensalidade int,
foreign key (id) references creditos(id));
And i have a table called:
CREATE TABLE public.creditos (
id serial NOT NULL,
veiculo varchar(10) NOT NULL,
matricula varchar(10) NOT NULL,
nome bpchar(30) NOT NULL,
telemovel varchar(10) NOT NULL,
valordevendapronto int4 NOT NULL,
juros int4 NULL,
valortotal int4 NULL,
entradainicial int4 NOT NULL,
primensalidade int4 NULL,
segmensalidade int4 NULL,
tercmensalidade int4 NULL,
quamensalidade int4 NULL,
quimensalidade int4 NULL,
sexmensalidade int4 NULL,
datainicial date NULL DEFAULT now(),
datafinal date NULL,
pago bpchar(3) NULL,
CONSTRAINT creditos_pkey PRIMARY KEY (id));
And my objective is after i insert on updates.primensalidade, it goes to creditos.primensalidade and change it to what i choosed before on updates.primensalidade where my creditos.matricula and updates.matricula are the same.
what i have soo far is:
CREATE OR REPLACE function creditoupdate()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
begin
insert into creditos(primensalidade) values(new.primensalidade) where matricula = new.matricula ;
return new;
end;
$function$
;
create trigger creditoupdatetrigger after
insert
on
updates for each row execute function creditoupdate();
I hope you can help me thx.

Answer 1

WHERE cannot be used in INSERT like that.
To to update primensalidade column in table creditos, the following can be used:
UPDATE creditos SET primensalidade = new.primensalidade where matricula = new.matricula;
More about UPDATE - https://www.postgresql.org/docs/current/sql-update.html
More about INSERT - https://www.postgresql.org/docs/current/sql-insert.html