having clause question

Hello,

I am attempting to convert a query from MySQL to PostgreSQL
and am having some trouble using an aggregate column in a
having clause. As a quick example, take the following SQL
script:

create table names(
firstname varchar(40) not null,
lastname varchar(40) not null
);

insert into names values('John','Smith');
insert into names values('Bob','Smith');
insert into names values('Mike','Skinner');

I want to retrieve any last names with more than 1
occurence in the table. Under MySQL, this query does the
trick.
select lastname,count(*) as c from names group by lastname
having c > 1;

But under PG, it errors out
ERROR: column "c" does not exist

Is it possible to do a query like this with PostgreSQL?

Thanks,
Shane

--
Shane Wegner
http://www.cm.nu/~shane/