MYSQL where statements -

i making system checks connectivity on ssl adresses. this, use 2 tables:

ssllist - id - dnsname - active (0 or 1)  sslresult - id - ssllist_id - starttime - result (0 or 1) 

by default, system checks entries in ssllist every 30 minutes, want check entries every minute match these rules:

- active=1 and(   - no results of entry in sslresult or   - had error in last half hour (result=0) or   - did not have results in last half hour ) 

so, made query comply first 3 rules:

select ssllist.id id, ssllist.dnsname ssllist left join sslresult on ssllist.id = sslresult.ssllist_id  ssllist.active=1  , (   (sslresult.result = 0 , sslresult.starttime > (unix_timestamp() - 1800)     or    sslresult.ssllist_id null ) group id 

however don't know how add last "where" statement, "get ssllist.id's did not have sslresult in last half hour).

how that?