Deletion Recursively

Greetings.

I am fairly new with the postgresql database.
And I have run into a problem, which I hope someone can help me with.

I am doing a school project, where I have chosen to learn to use this powerful tool, so I am using it to
handle a fictive company of banner advertising.

I need to register Advertisers, who got some Campaigns, and these campaigns have banners.
I have an Advertiser table, a campaign table and a banner table.

an advertiser hold references to the campaigns that he own, and the campaigns have references to the banners that they own.

My question is then: "How do I make the Database delete the campaigns and banners linked to the advertiser, when I delete him?"

A small example would really really help me alot.
(with small explanation too ofcause =) )

Yours, Michael.