trigger bag in sqlite3

CREATE TABLE "Customers"
(
    "id" integer,
    "name" text not null,
    "surname" text not null,
    "email" text not null unique,
    "orders" text,
    primary key ("id")
);

CREATE TABLE "Orders"
(
    "id" integer,
    "order_date" numeric not null default current_timestamp,
    "customer_id" numeric not null,
    "delivery_adress" text not null,
    primary key ("id"),
    foreign key ("customer_id") references "Customers"("id")
);

CREATE TRIGGER "purchase"
AFTER INSERT ON "Orders"
WHEN "customer_id" in (select "id" from "customers")
BEGIN
    UPDATE Customers
    SET orders = orders || ',' || new."id"
    WHERE id = new."customer_id";
END;