task History, SCD & as-of · hard

Build a country history from invoices

For identified customers whose invoices list more than one country, return customer_id, country, valid_from and valid_to: one row per run of consecutive invoices (by ordered_at, order_id) with the same country. valid_from is the run’s first invoice date; valid_to is the next run’s first invoice date, NULL for the last run.

what to return

Columns

customer_idcountryvalid_fromvalid_to in this order

Rows

13 rows · any order

Skill

Turn event snapshots into validity intervals. Refresher: Compare rows with LAG →

expected result

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

data you can query

Retail dataset: the first 6 rows of each table. Under each column name: the kind of value it holds, and which table it links to. Your queries run on all rows.