1174-Immediate-Food-Delivery-II.tsql

WITH FirstOrderDate AS(
    SELECT customer_id ,
    MIN(order_date) AS first_order_date
    FROM Delivery 
    GROUP BY customer_id 
)
SELECT 
ROUND(
        SUM(CASE WHEN d.order_date =customer_pref_delivery_date THEN 1 ELSE 0 END ) *100.0 / COUNT(*)
    ,2) AS immediate_percentage 
FROM Delivery d
JOIN FirstOrderDate f
ON d.order_date = f.first_order_date AND d.customer_id  = f.customer_id