Interview › Latest row

SQL interview: latest order per customer

MAX(order_date) then join back fails when two orders share that date. Number the rows.

Prompt. Return the most recent order row per customer (full row, not just the date).

Hint: ROW_NUMBER PARTITION BY customer_id ORDER BY order_date DESC

Your T-SQL

SELECT *
FROM (
  SELECT o.*,
         ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC, order_id DESC) AS rn
  FROM Orders o
) x
WHERE rn = 1;

CROSS APPLY (SELECT TOP 1 …) is the same idea and sometimes reads better.

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