Median Delivery Time per Dark Store

SQL practice question · Hard · Window Functions · Zepto

Compute the median delivery time per dark store WITHOUT using a MEDIAN or PERCENTILE function. Delivery minutes = (delivered_at - placed_at) in minutes (can be fractional). Orders with delivered_at NULL are not delivered and are excluded; stores with no delivered order are not shown. For an even count the median is the average of the two middle values. Return store_id, delivered_orders and median_minutes (ROUND to 1). Order by median_minutes DESC, then store_id.

Table: deliveries

Schema of deliveries
ColumnType
order_idINTEGER
store_idTEXT
placed_atTIMESTAMP
delivered_atTIMESTAMP
Sample rows of deliveries
order_idstore_idplaced_atdelivered_at
1S12026-07-01 10:00:002026-07-01 10:08:00
2S12026-07-01 11:00:002026-07-01 11:12:00
3S12026-07-01 12:00:002026-07-01 12:10:00
4S22026-07-01 10:00:002026-07-01 10:15:00
5S22026-07-01 10:30:002026-07-01 10:39:00
6S22026-07-01 11:00:002026-07-01 11:11:00
7S22026-07-01 12:00:002026-07-01 12:20:00
8S32026-07-01 09:00:002026-07-01 09:07:00
Expected output on the sample data
store_iddelivered_ordersmedian_minutes
S2413
S1310
S317

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