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BasicSQL~7 min

Customers who never placed an order

Asked in nearly every database testing interview

Points available

100/100

Your mission

  1. Read
  2. 2Run
  3. 3Submit
  4. 4Solve

Return id and name of customers that have no rows in orders.

Runs on the QA Shop practice database (customers, products, orders, order_items, payments, employees, bugs, test_runs, audit_log). Each run starts from a fresh copy.

Hints

Each hint costs 10 points on a full solve.

Interviewer follow-ups

  • Rewrite it using NOT EXISTS.
  • Why can NOT IN be risky with NULLs?

Ctrl+Enter to run · add Shift to submit

1
2
3
Tab inserts two spaces. Press Escape, then Tab, to leave the editor.
Terminal

$ sqlite3 qa-shop.db < solution.sql

Run executes the open file. Submit scores solution.sql against hidden tests.

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