INSERT [IGNORE] INTO TABLE

If I try to insert some row which in the table already exist thepostgre don't insert it and tell some error. Everything
ok.I'llinsert only if there is not the same (same key) record,else don't insert and don't tell me errors about it.In
MySQLis a switch [IGNORE]. 
 
            Thanx for help
                    Petr Jezek