题解 | #统计作答次数#

select
    count(1) as total_pv,
    sum(
        case
            when a.submit_time is not null
            and a.score is not null then 1
            else 0
        end
    ) as complete_pv,
    count(
        distinct case
            when a.submit_time is not null
            and a.score is not null then a.exam_id
            else null
        end
    ) as complete_exam_cnt
from
    exam_record a

你爱用if用if哈，我是不怎么喜欢if。因为以前遇到过很多复杂条件，if用着是真难受。