CREATE TABLE price_tiers (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    product_id UUID NOT NULL REFERENCES products(id) ON DELETE CASCADE,
    unit_id UUID NOT NULL REFERENCES units(id) ON DELETE RESTRICT,
    quantity NUMERIC(14, 3) NOT NULL CHECK (quantity > 0),
    price_cents BIGINT NOT NULL CHECK (price_cents >= 0),
    position INT NOT NULL DEFAULT 0,
    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE INDEX idx_price_tiers_product_id ON price_tiers(product_id);