# 1174.(Medium)即时食物配送 II

配送表: Delivery

```
+-----------------------------+---------+
| Column Name                 | Type    |
+-----------------------------+---------+
| delivery_id                 | int     |
| customer_id                 | int     |
| order_date                  | date    |
| customer_pref_delivery_date | date    |
+-----------------------------+---------+
delivery_id 是表的主键。
该表保存着顾客的食物配送信息，顾客在某个日期下了订单，并指定了一个期望的配送日期（和下单日期相同或者在那之后）。
```

如果顾客期望的配送日期和下单日期相同，则该订单称为 「即时订单」，否则称为「计划订单」。

「首次订单」是顾客最早创建的订单。我们保证一个顾客只会有一个「首次订单」。

写一条 SQL 查询语句获取**即时订单在所有用户的首次订单中的比例**。保留两位小数。

查询结果如下所示：

```
Delivery 表：
+-------------+-------------+------------+-----------------------------+
| delivery_id | customer_id | order_date | customer_pref_delivery_date |
+-------------+-------------+------------+-----------------------------+
| 1           | 1           | 2019-08-01 | 2019-08-02                  |
| 2           | 2           | 2019-08-02 | 2019-08-02                  |
| 3           | 1           | 2019-08-11 | 2019-08-12                  |
| 4           | 3           | 2019-08-24 | 2019-08-24                  |
| 5           | 3           | 2019-08-21 | 2019-08-22                  |
| 6           | 2           | 2019-08-11 | 2019-08-13                  |
| 7           | 4           | 2019-08-09 | 2019-08-09                  |
+-------------+-------------+------------+-----------------------------+

Result 表：
+----------------------+
| immediate_percentage |
+----------------------+
| 50.00                |
+----------------------+
1 号顾客的 1 号订单是首次订单，并且是计划订单。
2 号顾客的 2 号订单是首次订单，并且是即时订单。
3 号顾客的 5 号订单是首次订单，并且是计划订单。
4 号顾客的 7 号订单是首次订单，并且是即时订单。
因此，一半顾客的首次订单是即时的。
```

来源：力扣（LeetCode）

链接：<https://leetcode-cn.com/problems/immediate-food-delivery-ii>

著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

## Solution

window func

```sql
select 
    round(sum(order_date=customer_pref_delivery_date)/count(1)*100,2) 
    immediate_percentage
from (
    select *,
    row_number() over(partition by customer_id order by order_date) rk
    from Delivery
) t
where rk=1
```

subquery

```sql
select 
    round(sum(if(order_date=customer_pref_delivery_date,1,0))/count(distinct customer_id)*100,2) 
    immediate_percentage
from Delivery
where (customer_id, order_date) in 
            (select customer_id, min(order_date) 
            from Delivery
            group by customer_id);
```


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