将多个select [group by]查询与条件组合在一起

Question

我有3个选择查询，返回2列设置。 有quizno，correct，wrong和notattempted列可以像以下一样出现：

quizno  correct wrong   notattempted
1       80      10      10
2       60      20      20
3       100     0       0

这些是分开的查询：

select quizno, count(*) as correct from v_t1 where examid=96 AND result='correct'
group by quizno order by count(*) desc

select quizno, count(*) as wrong from v_t1 where examid=96 AND result='wrong'
group by quizno order by count(*) desc

select quizno, count(*) as notattempted from v_t1 where examid=96 AND result='notattempted'
group by quizno order by count(*) desc

Answer 1

您可以使用CASE聚合并获得预期的输出

select quizno,
       sum( case when result='correct' then 1 else 0 end) as 'correct',
       sum( case when result='wrong' then 1 else 0 end) as 'wrong',
       sum( case when result='notattempted' then 1 else 0 end) as 'notattempted'
from v_t1
where examid = 96
group by quizno