人生苦短，但求成长

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题解 | #月均完成试卷数不小于3的用户爱作答的类别#题目有歧义，当月均完成数定义不清

select tag,count(1) as tag_cnt from exam_record t1 join examination_info t2 on t1.exam_id = t2.exam_...

Mysql

2022-03-13

1 235

题解 | #未完成试卷数大于1的有效用户#主要是group_concat函数的用法

select uid, sum(if(submit_time is null,1,0)) as incomplete_cnt, ...

Mysql

2022-03-13

2 538

题解 | #未完成试卷数大于1的有效用户#题目说的不清不楚的，可以把两段和成一段

select t1.uid,incomplete_cnt,complete_cnt,detail from ( select ...

Mysql

2022-03-13

3 387

题解 | #月总刷题数和日均刷题数#主要是求每个月总有多少天

select * from ( select date_format(submit_time,'%Y%m') as submit_month, ...

Mysql

2022-03-13

10 452

题解 | #平均活跃天数和月活人数#注意求活跃天数时要把用户和日期去重

select date_format(start_time,'%Y%m') as month, round(count(distinct uid,date_for...

Mysql

2022-03-13

1 390

题解 | #得分不小于平均分的最低分#不小于就用大于或等于

select min(score) as min_score_over_avg from exam_record t1 join examination_info t2 on t1.exam_id ...

Mysql

2022-03-13

2 329

题解 | #统计作答次数#

select count(1) as total_pv, sum(if(score is not null,1,0)) ...

Mysql

2022-03-13

2 315

题解 | #SQL类别高难度试卷得分的截断平均值#

select tag,difficulty,round(avg(score),1) as clip_avg_score from( select tag,difficulty,score, ...

Mysql

2022-03-13

1 352

题解 | #删除索引#

drop index uniq_idx_exam_id on examination_info; drop index full_idx_tag on examination_info;

Mysql

2022-03-13

1 247

题解 | #创建索引#

create index idx_duration on examination_info(duration); create unique index uniq_idx_exam_id on examinat...

Mysql

2022-03-13

1 310