JanisZhan
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题解 | #获取员工其当前的薪水比其manager当前薪水还高的相关信息#
思路是先分别建立员工工资表和经理工资表,再连表查询 select e.emp_no,m.manager_no,e.emp_salary,m.manager_salary from ( select dm.dept_no,dm.emp_no as manager_no,s.salary...
Mysql
2022-06-30
1
154
题解 | #最差是第几名(一)#
利用 over( order by xxx) 计算每等级及以上的数量 select grade,sum(number) over(order by grade) as t_rank from class_grade
Mysql
2022-06-30
0
139
题解 | #牛客的课程订单分析(三)#
select * from order_info where date > '2025-10-15' and status = 'completed' and product_name in ('C++', 'Java', 'Python') and user_id in (select us...
Mysql
2022-06-29
0
137
题解 | #牛客的课程订单分析(二)#
要记得筛选 status 为 completed 的 表示订单成交成功的 select user_id from ( select user_id,count(1) as total from order_info where date>'2025-10-15' ...
Mysql
2022-06-29
1
168
题解 | #考试分数(二)#
建立一个表得出每个科目的平均分,再进行连表比较 select id,job,score from grade left join (select job as j,avg(score) as av from grade group by job) a on grade.job=a.j whe...
Mysql
2022-06-29
1
138
题解 | #异常的邮件概率#
直接先筛选出不是黑名单的用户(发送和接受者) select e.date, round(sum(case when e.type='no_completed' then 1 else 0 end)/count(*),3) as p from email e where e.send_id not...
Mysql
2022-06-28
1
187
题解 | #实习广场投递简历分析(二)#
选取月份补0方法: right(100+month(选取的月份),2) select job, concat(year(date),'-',right(100+month(date),2)) as mon, sum(num) as cnt from resume_info where year(da...
Mysql
2022-06-28
0
155
题解 | #实习广场投递简历分析(一)#
year(字段名) 可直接获取年份 select job, sum(num) as cnt from resume_info where year(date)=2025 group by job order by cnt desc
Mysql
2022-06-28
1
168
题解 | #获得积分最多的人(一)#
用Limite 查询出最大值 想问下大家为什么group by 要加name select u.name,sum(g.grade_num) as total from user u left outer join grade_info g on u.id=g.use...
Mysql
2022-06-28
1
117
题解 | #今天的刷题量(一)#
在mysql 中 可用 current_date表示当日的日期 select sj.name,count(*) as cnt from submission sb left outer join subject sj on sb.subject_id=sj.id where sb.crea...
Mysql
2022-06-28
1
139
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