-- https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/Model-Conditions.html
SELECT country, prod, year, s
  FROM sales_view_ref
  MODEL
    PARTITION BY (country)
    DIMENSION BY (prod, year)
    MEASURES (sale s)
    IGNORE NAV
    UNIQUE DIMENSION
    RULES UPSERT SEQUENTIAL ORDER
    (
      s['Mouse Pad', 2000] =
        CASE WHEN s['Mouse Pad', 1999] IS PRESENT
             THEN s['Mouse Pad', 1999]
             ELSE 0
        END
    )
  ORDER BY country, prod, year;