CREATE TABLE comments
(
    id NUMBER(2) NOT NULL,
    article_comment VARCHAR2(30),
    idarticle NUMBER(2),
    iduser NUMBER(2)
);

CREATE TABLE users
(
    id NUMBER(2) NOT NULL,
    username VARCHAR2(10),
    password VARCHAR2(10)
);

CREATE TABLE tags
(
    id NUMBER(2) NOT NULL,
    tagname VARCHAR2(10)
);

CREATE TABLE articles
(
    id NUMBER(2) NOT NULL,
    iduser NUMBER(2),
    title VARCHAR2(10),
    content VARCHAR2(10)
);

CREATE TABLE tags_articles
(
    idarticle NUMBER(2) NOT NULL,
    idtag NUMBER(2) NOT NULL
);

ALTER TABLE comments ADD CONSTRAINT pk_constraints PRIMARY KEY (id);
ALTER TABLE users ADD CONSTRAINT pk_users PRIMARY KEY (id);
ALTER TABLE tags ADD CONSTRAINT pk_tags PRIMARY KEY (id);
ALTER TABLE articles ADD CONSTRAINT pk_articles PRIMARY KEY (id);
ALTER TABLE tags_articles ADD CONSTRAINT pk_tags_articles PRIMARY KEY (idarticle, idtag);