-- *** before: ***
-- the history of a row was kept by hand: a shadow table
-- and a trigger that copied the old values into it

-- *** in version 2011: ***
CREATE TABLE city_history (
    ID         INTEGER PRIMARY KEY,
    Name       VARCHAR(35),
    Population INTEGER,
    Sys_start  TIMESTAMP GENERATED ALWAYS AS ROW START,
    Sys_end    TIMESTAMP GENERATED ALWAYS AS ROW END,
    PERIOD FOR SYSTEM_TIME (Sys_start, Sys_end)
) WITH SYSTEM VERSIONING

-- Support: MS SQL Server 2016 (it wants a HISTORY_TABLE named next to
-- the definition) and MariaDB 10.3. Oracle covers the same ground with
-- Flashback Data Archive rather than the standard syntax. MySQL,
-- PostgreSQL, SQLite, Firebird and Access have nothing of the kind.