[Exim] Getting Local Domains from mySQL

Heya people...

I'm using a modified version of the vmail-sql databases, and just now I
noted that the local_domain query doesn't get the domain aliases... for
knowing, the DB scheme (just the important fields)

table domain:
    field domain_name -> contains the domain name :)

table domain_alias:
    field alias -> contains the alias of the domain.
    field domain_name -> contains the domain being aliased (that exists in
the 'domain_name' field of the 'domain' table

example:

domain lasca-pinga.com exists in domain.domain_name
and
alias lascapinga.com points to lasca-pinga.com

the exim.conf contains:

domainlist local_domains = ${lookup mysql{select domain_name \
        from domain where domain_name = '$domain'}}

and if I try to send a mail to a alias domain, this query doesn't return
it as a local domain and I get a "Relay Denied"

Somebody can help me with the query?

thanks.