Immediate Food Delivery II

Task: Find the percentage of immediate orders in the first orders of all customers, rounded to 2 decimal places.

Table: Delivery

+-----------------------------+------+
| Column Name                 | Type |
+-----------------------------+------+
| delivery_id                 | INT  |
| customer_id                 | INT  |
| order_date                  | date |
| customer_pref_delivery_date | date |
+-----------------------------+------+

Input: Delivery table:

+-------------+-------------+------------+-----------------------------+
| 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                  |
+-------------+-------------+------------+-----------------------------+

Output:

+----------------------+
| immediate_percentage |
+----------------------+
| 50                   |
+----------------------+