---

-- Таблица студентов
CREATE TABLE students (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name VARCHAR(100) NOT NULL
);

-- Таблица преподавателей
CREATE TABLE teachers (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name VARCHAR(100) NOT NULL
);

-- Таблица предметов
CREATE TABLE subjects (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name VARCHAR(100) NOT NULL
);

-- Таблица оценок
CREATE TABLE grades (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    grade INTEGER NOT NULL,

    student_id INTEGER NOT NULL,
    teacher_id INTEGER NOT NULL,
    subject_id INTEGER NOT NULL,

    FOREIGN KEY (student_id) REFERENCES students(id),
    FOREIGN KEY (teacher_id) REFERENCES teachers(id),
    FOREIGN KEY (subject_id) REFERENCES subjects(id)
);