Laravel查询生成器常规错误2031

以下是使用Laravel查询构建器的查询：

$begin = new DateTime('2016-07-01');
$end = new DateTime('2016-07-31');
$startDate = $begin->format('Y-m-d 00:00:00');
$endDate = $end->format('Y-m-d 23:59:59');
$deposit = $depositModel->select(DB::raw('user_deposit.user_id as user_id, sum(user_deposit.amount) as total_deposit, null as total_withdraw'))
                        ->whereBetween('date_time', [$startDate, $endDate])
                        ->where('user_deposit.status', 1)
                        ->groupBy('user_deposit.user_id');
$withdraw = $withdrawModel->select(DB::raw('user_withdraw.user_id as user_id, null as total_deposit, sum(user_withdraw.amount) as total_withdraw'))
                        ->whereBetween('user_withdraw.created_at', [$startDate, $endDate])
                        ->where('user_withdraw.status', 1)
                        ->groupBy('user_withdraw.user_id');
$deposit = $deposit->unionAll($withdraw);
$transaction = DB::table(DB::raw("({$deposit->toSql()}) t"))
                  ->select('user_id', DB::raw("sum(total_deposit) as total_deposit_amount, sum(total_withdraw) as total_withdraw_amount"))
                  ->groupBy('user_id')
                  ->get();

我希望得到如下结果：

"transaction": [
            {
                "user_id": 2,
                "total_deposit_amount": "101.00",
                "total_withdraw_amount": "50.50"
            },
            {
                "user_id": 5,
                "total_deposit_amount": null,
                "total_withdraw_amount": "50.50"
            }
        ]

但后来我不断收到 SQLSTATE[HY000]: General error: 2031 . 所以我在查询上使用 toSql() 获取原始sql查询并尝试在MySQL中运行它并且它生成了如上所述的预期结果 .

下面是运行toSql（）后的查询

SELECT`user_id`, SUM(total_deposit) AS total_deposit_amount, SUM(total_withdraw) AS total_withdraw_amount 
FROM (( SELECT user_deposit.user_id AS user_id, SUM(user_deposit.amount) AS total_deposit, null AS total_withdraw 
        FROM `user_deposit` 
        WHERE`date_time` BETWEEN '2016-07-01' AND '2016-07-31' 
        AND `user_deposit`.`status` = 1 
        GROUP BY `user_deposit`.`user_id`) 
        UNION ALL (SELECT user_withdraw.user_id AS user_id, null AS total_deposit, SUM(user_withdraw.amount) AS total_withdraw 
                   FROM `user_withdraw` 
                   WHERE `user_withdraw`.`created_at` BETWEEN '2016-07-01' AND '2016-07-31' 
                   AND `user_withdraw`.`status` = 1
                   GROUP BY `user_withdraw`.`user_id`)) t 
        GROUP BY `user_id`

所以问题是，我的查询构建器出了什么问题？为什么原始sql在查询构建器不工作时有效？

谢谢