most idiomatic way to "update or insert"?

So I have some data that I want to put into a table.  If the
row already exists (as defined by the primary key), I would
like to update the row.  Otherwise, I would like to insert
the row.

I've been doing something like

delete from foo where name = 'xx';
insert into foo values('xx',1,2,...);

but I've been wondering if there's a more idiomatic or canonical
way to do this.

Many TIA,
Mark

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Mark Harrison
Pixar Animation Studios