Creating tables

DROP TABLE IF EXISTS ingredient_stock;
DROP TABLE IF EXISTS provider_ingredient;
DROP TABLE IF EXISTS pizza_ingredient;
DROP TABLE IF EXISTS ingredient;
DROP TABLE IF EXISTS provider;
DROP TABLE IF EXISTS order_item;
DROP TABLE IF EXISTS "order";
DROP TABLE IF EXISTS customer;
DROP TYPE  IF EXISTS order_status;
DROP TABLE IF EXISTS pizza;

CREATE TABLE pizza
(
    name   TEXT PRIMARY KEY,
    price  NUMERIC NOT NULL CHECK ( price > 0 ),
    weight NUMERIC NOT NULL CHECK ( weight > 0 )
);
CREATE TABLE ingredient
(
    id   INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    name TEXT NOT NULL UNIQUE
);
CREATE TABLE pizza_ingredient
(
    ingredient_id INT REFERENCES ingredient,
    pizza         TEXT REFERENCES pizza,
    weight        NUMERIC NOT NULL CHECK ( weight > 0 ),
    PRIMARY KEY (ingredient_id, pizza)
);
CREATE TABLE ingredient_stock
(
    ingredient_id INT PRIMARY KEY REFERENCES ingredient,
    weight        NUMERIC NOT NULL CHECK ( weight > 0 )
);
CREATE TABLE customer
(
    phone_number TEXT PRIMARY KEY CHECK ( phone_number ~ '^8[0-9]{10}$' ),
    discount     NUMERIC
);
CREATE TYPE order_status AS ENUM ('принят', 'в обработке', 'отгружен', 'выполнен');
CREATE TABLE "order"
(
    id       SERIAL       PRIMARY KEY,
    date     timestamp    NOT NULL,
    customer TEXT         NOT NULL REFERENCES customer,
    address  TEXT         NOT NULL,
    status   order_status NOT NULL
);
CREATE TABLE order_item
(
    order_id INT REFERENCES "order",
    pizza        TEXT REFERENCES pizza,
    count        INT NOT NULL,
    PRIMARY KEY (order_id, pizza)
);
CREATE TABLE provider
(
    id   INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    org_name     TEXT NOT NULL ,
    phone_number TEXT NOT NULL CHECK ( phone_number ~ '^8[0-9]{10}$' ),
    UNIQUE (org_name, phone_number)
);
CREATE TABLE provider_ingredient(
    provider_id INT REFERENCES provider,
    ingredient_id INT REFERENCES ingredient,
    price NUMERIC NOT NULL,
    PRIMARY KEY (provider_id, ingredient_id)
);