Commands

delete

update

insert

select

SELECT vs PERFORM vs CALL

A snag with writing procedures rather than functions is CALL procedurename(args) can’t be combined with FROM... WHERE clauses. A way around this in PL/PGSQL is to use PERFORM functioname(args) which acts like a procedure in that its result is ignored, so doesn’t require a dummy variable while opening the way for it to also be used as a normal query invoked by SELECT.

There are many tokens to tweak queries returning sets or aggregators.