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全部文章 / 题解（共155篇）

题解 | #插入记录（一）#

insert into exam_record (uid,exam_id,start_time,submit_time,score) values (1001,9001,'2021-09-01 22:11:12','2021-09-01 23:01:12',90), (1002,9002,'...

Mysql

2022-01-16

0 283

题解 | #创建索引#

create index idx_duration on examination_info(duration); create unique index uniq_idx_exam_id on examination_info(exam_id); create fulltext index full...

Mysql

2022-01-14

0 357

题解 | #统计作答次数# 来自专栏

select count(start_time) as total_pv, COUNT(submit_time) as complete_pv, #去除未完成的试卷 COUNT(distinct exam_id and score is not null) as comple...

Mysql

2022-01-14

0 270

题解 | #删除索引#

#sql中删除索引的语法 drop index uniq_idx_exam_id on examination_info; drop index full_idx_tag on examination_info;

Mysql

2022-01-14

0 309

题解 | #修改表#

#sql修改表结构的语法 alter table user_info add school varchar(15) after level; alter table user_info change job profession varchar(10); alter table user...

Mysql

2022-01-13

0 214

题解 | #查看不同年龄段的用户明细#

#sql中case when end的用法 select device_id,gender, case when age>=25 then '25岁及以上' when age>=20 then '20-24岁' else '其他' ...

Mysql

2022-01-12

0 269

题解 | #跳台阶扩展问题#

public: int jumpFloorII(int number) { //使用递归的暴力解法 int shu[20]={0}; shu[0]=1; shu[1]=1; shu[2]=2; i...

C++

2022-01-11

0 252

题解 | #二叉搜索树的第k个节点#

* struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {} * ...

C++

2022-01-11

0 313

题解 | #删除记录（二）#

delete from exam_record where submit_time is null #sql中使用timestampdiff函数获取时间差 or timestampdiff(minute,start_time,submit_time)<5 order b...

Mysql

2022-01-10

0 228

题解 | #计算用户8月每天的练题数量#

#使用sql中的substring_index字符串截取函数 SELECT SUBSTRING_INDEX(date,"-",-1) as day, count(question_id) as question_cnt from question_practice_detail where ...

Mysql

2022-01-09

0 278