text: --1173. Immediate Food Delivery I
  --
  --Table: Delivery
  --+-----------------------------+---------+
  --| Column Name                 | Type    |
  --+-----------------------------+---------+
  --| delivery_id                 | int     |
  --| customer_id                 | int     |
  --| order_date                  | date    |
  --| customer_pref_delivery_date | date    |
  --+-----------------------------+---------+
  --delivery_id is the primary key of this table.
  --The table holds information about food delivery to customers that make orders at some date and specify a preferred delivery date (on the same order date or after it).
  --If the preferred delivery date of the customer is the same as the order date then the order is called immediate otherwise it's called scheduled.
  --
  --Write an SQL query to find the percentage of immediate orders in the table, rounded to 2 decimal places.
  --The query result format is in the following example:
  --Delivery table:
  --+-------------+-------------+------------+-----------------------------+
  --| delivery_id | customer_id | order_date | customer_pref_delivery_date |
  --+-------------+-------------+------------+-----------------------------+
  --| 1           | 1           | 2019-08-01 | 2019-08-02                  |
  --| 2           | 5           | 2019-08-02 | 2019-08-02                  |
  --| 3           | 1           | 2019-08-11 | 2019-08-11                  |
  --| 4           | 3           | 2019-08-24 | 2019-08-26                  |
  --| 5           | 4           | 2019-08-21 | 2019-08-22                  |
  --| 6           | 2           | 2019-08-11 | 2019-08-13                  |
  --+-------------+-------------+------------+-----------------------------+
  --
  --Result table:
  --+----------------------+
  --| immediate_percentage |
  --+----------------------+
  --| 33.33                |
  --+----------------------+
  --The orders with delivery id 2 and 3 are immediate while the others are scheduled.
  
  
  # Write your MySQL query statement below
  select round(
      (
      100 * (select count(*) from Delivery d where d.order_date = d.customer_pref_delivery_date)/
          (select count(*) from Delivery)
          ),
      2) as immediate_percentage;