CODING EXERCISES
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SQLadvanced
Decrement stock when an order line lands
Attach an AFTER INSERT trigger on order_lines that subtracts NEW.qty from products.stock. Then insert order 3 for Ada buying one MUG-9 at 900 cents, and return mug stock plus the new line. Do not replay the trigger on the historical PEN-2 line: create the trigger after the seed.
SQLadvanced
Rank customers by spend without collapsing rows
Return every customer with spent_cents and spend_rank. spent_cents is the sum of qty * unit_cents across their lines, or 0 if they never ordered. Rank by spent_cents descending using RANK() so ties share a rank. Order the result by spend_rank, then display_name.