oj-sql

题目

SQL124 统计作答次数

思路

1. count sum if；

solution

count sum if

select
    count(exam_id) total_pv,
    sum(if(submit_time is null or score is null,0,1)) complete_pv,
    count(distinct if(submit_time is not null, exam_id,null)) complete_exam_cnt
from exam_record;