6. Orders with no payment
Asked in screens shaped like: PayPal, Capital One, Stripe
Every order should have a payment row. Find the ones that do not. This is the anti-join interviewers use to see whether you reach for NOT IN, which silently returns nothing when the subquery contains a NULL.
Requirements
- Columns: order_id, amount
- Return only orders with no matching payments row
- Order by order_id
- Do not use NOT IN
Expected output
order_id, amount
Row order is graded, so ORDER BY matters here.
Tables this problem reads. The full warehouse is available in thesandbox.
orders
~200 rows
Order headers. One row per order, so amount is the order total — not a line total.
- order_idINTEGER— 1000–1199
- customer_idTEXT— C01–C12
- countryTEXT— US, DE, IN, UK, BR
- amountREAL
- statusTEXT— 'completed' or 'cancelled'
- ordered_atTEXT— YYYY-MM-DD HH:MM:SS
payments
~182 rows
Settlements. Cancelled orders have no payment row, which is the anti-join case.
- payment_idINTEGER
- order_idINTEGER— joins orders
- methodTEXT— card, ach, wallet
- amountREAL
- paid_atTEXT
Pick a warehouse dialect above the editor. The engine is still SQLite; common syntax is rewritten before it runs.
SQLite cheat sheet
- Truncate to day
DATE(ordered_at) - Current date
DATE('now') - Conditional
CASE WHEN … THEN … ELSE … END - String aggregate
GROUP_CONCAT(col, ", ") - JSON field
json_extract(payload, '$.source') - Date difference
JULIANDAY(a) - JULIANDAY(b) - Filter a window
CTE, then WHERE rn = 1 - Median
ROW_NUMBER + COUNT(*) OVER ()
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