题解 | #统计作答次数#
统计作答次数
http://www.nowcoder.com/practice/45a87639110841b6950ef6a12d20175f
SELECT COUNT(exam_id) total_pv, COUNT(submit_time) complete_pv, COUNT(DISTINCT IF(submit_time IS NOT NULL, exam_id, NULL)) complete_exam_cnt FROM exam_record;
统计作答次数
http://www.nowcoder.com/practice/45a87639110841b6950ef6a12d20175f
SELECT COUNT(exam_id) total_pv, COUNT(submit_time) complete_pv, COUNT(DISTINCT IF(submit_time IS NOT NULL, exam_id, NULL)) complete_exam_cnt FROM exam_record;
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