sql - PosgresSQL Trigger -

when new row inserted table forumtopics (cols: id | userid), want trigger makes insert table upvotes, uses id , userid forumtopics row.

so upvotes table look: id | userid | forumtopicsid (id original insert)

how may this?

first, create trigger function, e.g. (assuming upvotes.id of type serial):

create or replace function before_insert_on_forumtopics() returns trigger language plpgsql $$ begin     insert upvotes (userid, forumtopicsid)     values (new.userid, new.id);     return new; end $$; 

next, create trigger:

create trigger before_insert_on_forumtopics before insert on forumtopics each row  execute procedure before_insert_on_forumtopics(); 

read in documentation trigger behavior, trigger procedures , create trigger.