CREATE TABLE dbo.GROUPS
(
    groupname VARCHAR(50) PRIMARY KEY
);

CREATE TABLE dbo.STUDENTS
(
    username VARCHAR(50) PRIMARY KEY,
    password VARCHAR(50) NOT NULL,
    fullname VARCHAR(MAX) NOT NULL,
    username_ia VARCHAR(50) NULL,
    username_pbinfo VARCHAR(50) NULL,
    username_timus VARCHAR(50) NULL,
    username_codeforces VARCHAR(50) NULL,
    groupname VARCHAR(50) FOREIGN KEY REFERENCES GROUPS(groupname) ON DELETE CASCADE ON UPDATE CASCADE
);


CREATE TABLE dbo.PROBLEMS
(
    id_problema VARCHAR(50) PRIMARY KEY,
    site VARCHAR(MAX) NOT NULL
);

CREATE TABLE dbo.SOLVED
(
    FK_username VARCHAR(50) FOREIGN KEY REFERENCES STUDENTS(username) ON DELETE CASCADE ON UPDATE CASCADE,
    FK_id_problema VARCHAR(50) FOREIGN KEY REFERENCES PROBLEMS(id_problema) ON DELETE CASCADE ON UPDATE CASCADE,
    CONSTRAINT PK_SOLVED PRIMARY KEY (FK_username, FK_id_problema)
);

CREATE TABLE dbo.SCHEDULE
(
    cod INT PRIMARY KEY,
    DAY DATE NOT NULL,
    HOUR TIME NOT NULL,
    username VARCHAR(50) FOREIGN KEY REFERENCES STUDENTS(username) ON DELETE CASCADE ON UPDATE CASCADE,
);