平凡的人5

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题解 | #按照数量和价格排序#

select quantity ,item_price from OrderItems order by quantity desc ,item_price desc; 1、单列排序，默认升序，降序后面接"DESC"即可 2、多列排序，首先按字段一字段排序，若字段一相等，则按字段二排序 3、自定义排...

Mysql

2022-04-26

0 451

题解 | #提取博客URL中的用户名#

select device_id,substring(blog_url,11) user_name from user_submit /* 一、mysql截取字符串函数 1、left(str,length) 从左边截取length 2、right(str,length)从右边截取length 3、...

Mysql

2022-04-26

0 393

题解 | #21年8月份练题总数#

用户数根据用户分组题目总数，？未分组？ select count(did_cnt) , sum(question_cnt) from (select count(device_id) did_cnt,count(question_id) question_cnt from question_p...

Mysql

2022-04-26

0 256

题解 | #分组排序练习题#

select university , avg(question_cnt) avg_question_cnt from user_profile group by university order by avg_question_cnt; 认真审题，发现没有注意到排序

Mysql

2022-04-26

0 249

题解 | #分组过滤练习题#

select university,avg(question_cnt) avg_question_cnt,avg(answer_cnt) avg_answer_cnt from user_profile group by university having avg_question_cnt <...

Mysql

2022-04-26

0 245

题解 | #查找最晚入职员工的所有信息#

/不会日期函数了，用一个子查询/ select emp_no ,birth_date, first_name, last_name, gender, hire_date from employees where hire_date=(select max(hire_date) from employ...

Mysql

2022-04-16

1 228

题解 | #分组计算练习题#

/* 我总感觉这么写怪怪的，group by 有的学一下啊*/ select gender ,university ,count(1) as user_num, sum(active_days_within_30)/count(1) as avg_active_day, sum(question_c...

Mysql

2022-04-15

0 277