Data Cleaning Exercises

Learning path · Visual

Beginner: clean data visually

Learn the core moves (trim, missing values, mappings, duplicates, joins) by building pipelines step by step, with a ledger of what each step changed.
  1. 1.

    Lesson · 8 min

    Profile before you change anything

    Read the data before changing it.

  2. 2.

    Lesson · 8 min

    Trim the right characters, and only those

    Trim the characters the rules name.

  3. 3.

    Exercise · beginner

    Normalize emails under a declared policy

    A two-step policy you can run twice.

  4. 4.

    Lesson · 8 min

    Missing is not empty (and neither is zero)

    Missing, empty and zero are different.

  5. 5.

    Exercise · beginner

    Label unknown categories, keep missing numbers missing

    Label categories, keep measurements missing.

  6. 6.

    Lesson · 9 min

    Map categories with an approved dictionary

    Map spellings with an approved dictionary.

  7. 7.

    Exercise · beginner

    Map channels with an approved dictionary

    Quarantine what the dictionary doesn't cover.

  8. 8.

    Lesson · 10 min

    Joins where missing keys never match

    Missing keys never match.

  9. 9.

    Exercise · beginner

    Join orders to customers without matching blanks

    Your first lookup.

  10. 10.

    Lesson · 10 min

    Find the row grain before removing duplicates

    Find the row grain.

  11. 11.

    Exercise · beginner

    Pick one surviving record per account

    Pick a surviving record.

  12. 12.

    Exercise · intermediate

    Clean an order-line export

    Put it together on a real-looking export.