sqlzoo练习15-null-quiz

select teacher.name, dept.name
from teacher
left outer join dept on (teacher.dept=dept.id) -- 左连接

select dept.name
from teacher
join dept on (dept.id=teacher.dept)
where teacher.name='Cutflower';

select dept.name, count(teacher.name)  -- 统计老师的个数
from teacher
right join dept on dept.id=teacher.dept
group by dept.name

display 0 in result column for all teachers without department

select name,
     case when phone=2752 then 'two'
          when phone=2753 then 'three'
          when phone=2754 then 'four'
     end as digit
from teacher

select name,
    case when dept in (1)
         then 'Computing'  -- 如果dept编号是1，则标记为computing；否则是Other
    else 'Other' end
from teacher;