Frequently Bought Together Pairs

SQL practice question · Hard · Analytics · Walmart, Amazon

Find product pairs that appear together in at least 2 different orders. A SKU listed twice in the same order counts once, and NULL SKUs are ignored. Return `sku_a`, `sku_b` (alphabetically sku_a < sku_b), `orders_together`, and `pct_of_orders` = ROUND(100.0 * orders_together / total orders, 1), where total orders = number of distinct orders containing at least one non-NULL SKU. Order by `orders_together` DESC, then `sku_a`, `sku_b`.

Table: basket_lines

Schema of basket_lines
Column	Type
order_id	INTEGER
sku	TEXT

Schema of basket_lines

Column

Type

order_id

INTEGER

sku

TEXT

Sample rows of basket_lines
order_id	sku
1	MILK
1	BREAD
1	EGGS
2	MILK
2	BREAD
3	MILK
3	EGGS
4	BREAD

Sample rows of basket_lines

order_id

sku

MILK

BREAD

EGGS

MILK

BREAD

MILK

EGGS

BREAD

Expected output on the sample data
sku_a	sku_b	orders_together	pct_of_orders
BREAD	MILK	3	60
EGGS	MILK	2	40

Expected output on the sample data

sku_a

sku_b

orders_together

pct_of_orders

BREAD

MILK

EGGS

MILK

Solve it in the live editor on this page — run on sample data, then submit against hidden tests.

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