Temporal databases let you record history: either a history of the database (what the table used to say), a history of the thing itself (what it used to be), or both at once.

This talk will cover temporal primary keys, foreign keys, updates, deletes, and joins: what they are, how to perform them in SQL:2011 (and coming soon in Postgres!), and how to implement operations not yet covered by the standard, like outer joins, semijoins, and antijoins.

I'll discuss my work adding application-time to Postgres, which was briefly part of v17 and will hopefully be complete for v18.