Problem 6 of 12 · Deduplication & Latest RowNext: Keep the latest payment per order

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Practice / SQL / Deduplication & Latest Row

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MediumAbout 10 minDeduplication & Latest RowLesson: Deduplication & Latest Row (P18) →

Keep the most complete row per customer

Per customer, keep the row with the fewest NULLs across email and phone (break ties by earliest loaded_ts). Sort by customer_id.

Returncustomer_idemailphone

Columns

dupes4 columns

columntype

customer_idVARCHAR

emailVARCHAR

phoneVARCHAR

loaded_tsTIMESTAMP WITH TIME ZONE

The table

14 rows · 4 columns

dupesfirst 5 of 14 rows

customer_idemailphoneloaded_ts

c_001alice@old.com+1-111-11112026-05-01 10:00:00

c_001alice@new.comNULL2026-05-15 10:00:00

c_001NULL+1-111-22222026-05-20 10:00:00

c_002bob@example.com+1-222-22222026-06-01 09:00:00

c_003carol@example.com+1-333-33332026-04-01 08:00:00

If you get stuck

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