Orders that were never returned

Constraints

1. 1An order counts as never returned when no row in shop_returns points at it.
2. 2The unmatched return row does not tell you anything about any particular order, so it must not remove orders from the answer.
3. 3Return the order's customer_id and order_total alongside its id.
4. 4Six of the twelve orders qualify.

Worked example

Order 1003 has no row anywhere in shop_returns, so it belongs in the answer alongside 1005, 1006, 1009, 1010 and 1012 — six orders in total. The obvious query is WHERE order_id NOT IN (SELECT order_id FROM shop_returns), and on this data it returns no rows at all. Return 5 carries a NULL order_id, and NOT IN expands to a chain of <> comparisons in which comparing anything to NULL is unknown rather than true. One unknown is enough to stop the whole chain being true, so even order 1003 is rejected.

What this tests

Why NOT IN is unsafe against a nullable column, and that NOT EXISTS expresses the same anti-join without the three-valued-logic trap.