On-Time Rate per Courier

For every courier compute the percentage of deliveries made on or before the promised date, rounded to 2 decimals. Order by courier.

Table schema

Deliveries(id INT PRIMARY KEY, courier VARCHAR(10), promised_date DATE, delivered_date DATE)

Sample data

id | courier | promised_date | delivered_date
1 | A | 2026-05-01 | 2026-05-01
2 | A | 2026-05-02 | 2026-05-04
3 | A | 2026-05-03 | 2026-05-02
4 | B | 2026-05-05 | 2026-05-05
5 | B | 2026-05-06 | 2026-05-05