SQL interview: rows to columns (PIVOT / CASE)

Wide reports are either PIVOT or a handful of SUM(CASE). Interviewers accept both. CASE is easier to read.

Prompt. One row per customer, columns for Shipped, Cancelled, Processing sales.

Hint: SUM(CASE WHEN status = … THEN amount ELSE 0 END)

Your T-SQL

SELECT customer_id,
       SUM(CASE WHEN status = 'Shipped' THEN total_amount ELSE 0 END) AS shipped,
       SUM(CASE WHEN status = 'Cancelled' THEN total_amount ELSE 0 END) AS cancelled,
       SUM(CASE WHEN status = 'Processing' THEN total_amount ELSE 0 END) AS processing
FROM Orders
GROUP BY customer_id;

Dynamic statuses: /tools/pivot. Do not concatenate user text into PIVOT IN.

Then write it on a ticket

Monday is free. A colleague asks, you type, we mark it.

Clock in free