Problem 1 of 5 · Slowly-changing dimensionsNext: Distinct email versions per customer

00:00

Practice / SQL / Slowly-changing dimensions

WorkingGuided

EasyAbout 12 minSlowly-changing dimensions

Type-1 current snapshot from a change log

From the dupes change log, build a Type-1 customer dimension — just the current email per customer (the latest non-NULL email by loaded_ts). Ignore NULL emails.

Sort by customer_id.

Returncustomer_idcurrent_email

Columns

dupes4 columns

columntype

customer_idVARCHAR

emailVARCHAR

phoneVARCHAR

loaded_tsTIMESTAMP WITH TIME ZONE

The table

9 rows · 4 columns

dupesfirst 5 of 9 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

Show hint · 1 hint Walkthrough Reveal answer

Your query · runs in your browser⌘ Enter to run

Loading editor…

Output · run to see rows