task Deduplication · medium

Keep one account per email

Treat emails as equal after trimming spaces and lowercasing. For each email, keep the shopper who signed up first. Return id, name and clean_email for the kept shoppers.

what to return

Columns

idnameclean_email in this order

Rows

14 rows · any order

Watch for

Ties on signup_date go to the lower id.

Shoppers with no email are excluded.

Skill

Deduplicate by a cleaned key, keeping a defined survivor. Refresher: Clean strings & cast values →

expected result

Your query should return exactly these columns and values. Run it and compare.

data you can query

Sample rows from each table. Each column shows its type underneath; → marks a link to another table.