[Exim] Condition for Exiscan?

Shouldnt the following work?

${lookup mysql{select VirusCheckIn from \
pm_users, pm_domains where pm_users.SiteID=pm_domains.ID \
AND pm_users.Name='$local_part' AND pm_domains.Name='$domain' \
AND VirusCheckIn = 'true'}{1}{0}}

Yet, when running debug i see

18396 type=mysql key="select VirusCheckIn from pm_users, pm_domains
where pm_users.SiteID=pm_domains.ID AND pm_users.Name='' AND
pm_domains.Name='' AND VirusCheckIn = 'true'"
18396 database lookup required for select VirusCheckIn from pm_users,
pm_domains where pm_users.SiteID=pm_domains.ID AND pm_users.Name='' AND
pm_domains.Name='' AND VirusCheckIn = 'true'
18396 MYSQL query: select VirusCheckIn from pm_users, pm_domains where
pm_users.SiteID=pm_domains.ID AND pm_users.Name='' AND
pm_domains.Name='' AND VirusCheckIn = 'true'
18396 MYSQL new connection: host=localhost port=0 socket=NULL
database=xams user=xams
18396 MYSQL: no data found

Does this mean that those variables aren't available to Exiscan? Or am I
screwing something else up?