CREATE TABLE IF NOT EXISTS tuition_zalo_history_tb (
    id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
    class_id INT NOT NULL,
    student_id INT NOT NULL,
    actor_id INT NOT NULL,
    phone VARCHAR(20) NOT NULL,
    message TEXT NOT NULL,
    kind VARCHAR(20) NOT NULL DEFAULT 'reminder',
    sent_at DATETIME NOT NULL,
    INDEX idx_student_class_sent (student_id, class_id, id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;