Delivery SLA by Meal Band

SQL practice question · Hard · Date & Time · Swiggy

Classify each order by the hour of `placed_at`: hours 12-14 -> 'Lunch', hours 19-22 -> 'Dinner', anything else -> 'Off-peak'. An order is on time if it was delivered (`delivered_at` not NULL) and the minutes from placed_at to delivered_at are <= `promised_min`. Undelivered orders are late. Return `band`, `total_orders`, `on_time_orders`, `on_time_pct` (ROUND 1), `avg_delay_min` = average of (actual minutes - promised_min) over LATE orders that WERE delivered (ROUND 1; NULL if there are none). Order by `on_time_pct` DESC, then `band`.

Table: deliveries

Schema of deliveries
ColumnType
order_idINTEGER
restaurant_idINTEGER
placed_atTIMESTAMP
delivered_atTIMESTAMP
promised_minINTEGER
Sample rows of deliveries
order_idrestaurant_idplaced_atdelivered_atpromised_min
112026-08-01 12:10:002026-08-01 12:40:0030
212026-08-01 13:00:002026-08-01 13:50:0035
322026-08-01 14:59:002026-08-01 15:20:0030
422026-08-01 19:00:002026-08-01 19:45:0040
532026-08-01 20:00:00NULL30
632026-08-01 22:30:002026-08-01 22:55:0030
712026-08-01 16:00:002026-08-01 16:20:0025
822026-08-01 11:59:002026-08-01 12:30:0030
Expected output on the sample data
bandtotal_orderson_time_orderson_time_pctavg_delay_min
Lunch3266.715
Off-peak21501
Dinner3133.35

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