INSERT OR UPDATE WITHOUT SELECT

[wmiro@xxxxxxxxx <wmiro@xxxxxxxxx>]

Hi, 

Is there a command to Insert a record If It does not exists and a update if 
It exists? 

I do not want to do a select before a insert or update. 

I mean the postgres should test if a record exist before insert and if It 
exist then the postgres must do an update instead an insert. 

Thanks, 

WMiro.