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CREATE TABLE studio (
name VARCHAR(256) primary key
);
CREATE TABLE author (
author_id NUMBER(10) primary key,
name VARCHAR(32) NOT NULL,
surname VARCHAR(32) NOT NULL,
birthdate DATE NULL,
gender VARCHAR(1) NULL ,
CONSTRAINT author_gender_constraint  CHECK ((gender IN ('K', 'M') OR gender IS NULL))
);

CREATE TABLE ilustrator(

)

CREATE TABLE manga(
id NUMBER(10) PRIMARY KEY,
title VARCHAR(256) NOT NULL,
genre VARCHAR(256) NULL,
volumes NUMBER(3) NULL,
chapters NUMBER(5) NULL,
publishing_type VARCHAR(256) NULL,
published_date DATE NULL,
author_id NUMBER(10) NOT NULL,
ilustrator_id NUMBER(10) NULL,
CONSTRAINT publishing_type_constraint CHECK ((publishing_type IN ('WEEKLY','DAILY','MONTHLY') OR publishing_type IS NULL)),
CONSTRAINT fk_author_id FOREIGN KEY (author_id) REFERENCES author(author_id),
CONSTRAINT fk_ilustrator_id FOREIGN KEY (ilustrator_id) REFERENCES ilustrator(ilustrator_id),
CONSTRAINT volumes_number_constraint CHECK (volumes IS NULL OR volumes > 0),
CONSTRAINT chapters_number_constraint CHECK (chapters IS NULL OR chapters > 0)
);