Fixed typo and change sql query

Fixed typo and change sql query for better search results, issue #1 
@qianlifeng it's case statement in ```order by```, equal:
```
select * 
from searchIndex 
where name like '%header%' 
order by
   case
      when name = 'header' then 1
   end desc,
   case
      when name like 'header%' then 1
   end desc
```

I think so =)