CREATE TABLE IF NOT EXISTS `billingMonthly` (
    `id` INT AUTO_INCREMENT PRIMARY KEY,
    `projectId` INT NOT NULL,
    `month` DATE NOT NULL,
    `amount` DECIMAL(10, 2) NOT NULL DEFAULT 0.00,
    FOREIGN KEY (`projectId`) REFERENCES `projects`(`id`) ON DELETE CASCADE,
    UNIQUE KEY `project_month` (`projectId`, `month`)
);