create table lesson (
    id number not null,
    number_lesson number,
    time_start varchar(100),
    time_end varchar(200),
    name varchar (50),
    constraint lesson_pk primary key (id)
);

create table day_week (
    id number not null,
    day_week varchar (50),
    constraint day_pk primary key (id)
);

create table study_group (
    id number not null,
    name varchar (50),
    constraint group_pk primary key (id)
);

create table cind_lesson (
    id number not null,
    name varchar (50),
    constraint cind_pk primary key (id)
);

create table subject (
    id number not null,
    name varchar (50),
    constraint subject_pk primary key (id)
);

create table audience (
    id number not null,
    name varchar (50),
    constraint audience_pk primary key (id)
);

create table sheldule (
    id number not null,
    day_week number not null,
    lesson number not null,
    study_group number not null,
    subject number not null,
    cind_lesson number not null,
    audience number not null,
    CONSTRAINT sheldule_pk PRIMARY KEY (id),
    CONSTRAINT fk_day_week_id
        FOREIGN key (day_week)
        references day_week (id),
    CONSTRAINT fk_lesson_id
        FOREIGN key (lesson)
        references lesson (id),
    CONSTRAINT fk_group_id
        FOREIGN key (study_group)
        references study_group (id),
    CONSTRAINT fk_subject_id
        FOREIGN key (subject)
        references subject (id),
    CONSTRAINT fk_cind_id
        FOREIGN key (cind_lesson)
        references cind_lesson (id),
    CONSTRAINT fk_audience_id
        FOREIGN key (audience)
        references audience (id)
);