Какие есть онлайн-тесты на знание SQL-запросов?

select 
  strftime('%Y-%m-%d %H:%M:%S', datetime(messages.timestamp, 'unixepoch')) as date,  
  chats.topic,
  contacts.displayname as author_name,
  messages.body_xml as message,
  messages.dialog_partner
from messages
left join chats          ON messages.convo_id = chats.conv_dbid
left join contacts       ON messages.author = contacts.skypename
where 
   body_xml like '%http%'
   and
   messages.dialog_partner is not null
group by messages.id