Data Cleaning Exercises

Learning path · SQL

Interview ready: explain every decision

Solve take-home style exercises, then practise explaining the trade-offs with the interview question bank.
  1. 1.

    Lesson · 10 min

    Hand off a cleaning job: rules, exceptions, reconciliation

    What a handoff contains.

  2. 2.

    Exercise · intermediate

    Clean an order-line export

    The classic take-home.

  3. 3.

    Lesson · 10 min

    Compare instants, not timestamp text

    Instants versus text.

  4. 4.

    Exercise · intermediate

    Timestamps need an offset

    Quarantine missing offsets.

  5. 5.

    Lesson · 10 min

    Merge on evidence, review the rest

    Evidence and review queues.

  6. 6.

    Exercise · intermediate · Pro

    Resolve customer records by normalized email

    Merge on evidence.

  7. 7.

    Lesson · 9 min

    Ranges and the order of rules

    Rule order and ranges.

  8. 8.

    Exercise · intermediate

    Validate quantities and prices against ranges

    Ordered validation.

  9. 9.

    Exercise · intermediate · Pro

    Sum amounts by currency, without converting

    Never add currencies.