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题解 | #顾客登录名#

select cust_id,cust_name, // 1.转大写2.字符串拼接3.字符串截取：substring(列,起始位置,结束位置)，起始位置下标为1 upper(concat(substring(cust_contact,1,2),substring(cust_city...

Mysql

2022-03-25

0 311

题解 | #纠错2#

select prod_name,prod_desc from Products # where prod_desc like '%toy%' and prod_desc like '%carrots%';#行 # where prod_desc like '%toy%' and '%carrots...

Mysql

2022-03-25

163 4661

题解 | #返回所有价格在 3美元到 6美元之间的产品的名称和价格#

select prod_name,prod_price from Products where prod_price between 3 and 6 order by prod_price;//默认升序

Mysql

2022-03-25

0 309

题解 | #检索并列出已订购产品的清单#

select order_num,prod_id,quantity from OrderItems where prod_id in('BR01','BR02','BR03') and quantity >= 100; 注意：prod_id 是字符串类型

Mysql

2022-03-25

0 345

题解 | #按照数量和价格排序#

select quantity,item_price from OrderItems order by quantity desc,item_price desc; //多列排序时,注意:1.注意列的顺序 2.注意格式：列1 asc/desc,列2 asc/desc...... //3.没有注明升降...

Mysql

2022-03-23

32 1002

题解 | #对顾客ID和日期排序#

select cust_id,order_num from Orders # 注意审题：订单日期倒序排列 order by cust_id asc,order_date desc; // order by + 列（select 后可以没有）

Mysql

2022-03-23

10 775

题解 | #21年8月份练题总数#

select count(distinct device_id) as did_cnt,//总用户数：用户可以登录多次同一台设备 count(question_id) as question_cnt//总次数 from question_practice_detail qpd where year...

Mysql

2022-03-23

4 330

题解 | #统计复旦用户8月练题情况#

select difficult_level, //正确率：正确数/总题数 sum(if(qpd.result = 'right', 1, 0)) / count(qpd.question_id) as correct_rate from question_practice_de...

Mysql

2022-03-23

6 500

题解 | #统计复旦用户8月练题情况#

select up.device_id, university, //是八月份计数+1（从0开始）,不是计数+0 sum(if(month(qpd.date) = 8,1,0)) as question_cnt, //答题结果正确计数+1，错误+0（同上）...

Mysql

2022-03-22

0 318

题解 | #找出每个学校GPA最低的同学#

select device_id, university, gpa from ( //*是为了提供select的列数据 //窗口函数：先根据university分组，然后在分组内部按gpa升序排列，这里取到的是不同学校升序排列的gpa数据们...

Mysql

2022-03-21

5 362