tasks/readable/009/task_readable.md

Task: 009

Database: retails

Question

List the customer who made the highest number of purchases using rail shipping.

Gold Query

WITH customer_rail_lineitems AS (
SELECT c.c_custkey,
c.c_name,
COUNT(*) AS rail_ship_count
FROM customer c
JOIN orders o ON c.c_custkey = o.o_custkey
JOIN lineitem l ON o.o_orderkey = l.l_orderkey
WHERE l.l_shipmode = 'RAIL'
GROUP BY c.c_custkey, c.c_name
)
SELECT c.c_custkey, c.c_name, c.rail_ship_count
FROM customer_rail_lineitems c
WHERE c.rail_ship_count = (
SELECT MAX(rail_ship_count) FROM customer_rail_lineitems
);

Execution Result:

c_custkey	c_name	rail_ship_count
63035	Customer#000063035	28

1 rows