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题解 | #获取employees中的first_name#

select first_name from employees //right(字段名，数值）表示从右边开始，选取字段“数值”位 //同理 left（字段名，数值）表示从左边开始选取 order by right(first_name,2)

Mysql

2022-06-27

0 198

题解 | #查找字符串中逗号出现的次数#

select id, //用原字符串的长度减去除去了逗号的字符串长度，得到逗号出现的次数 // length(string) 计算字符串的长度 //replace(string,'被替换的字符','用于替换的字符'） //在这里我们用空替换逗号 length(string)-l...

Mysql

2022-06-27

1 307

题解 | #将employees表中的所有员工的last_name和first_name通过引号连接起来。#

concat 用于连接 concat（字符1，字符2） //若连接符号，用引号括起，如横杆 '-' select concat(last_name,"'",first_name) as name from employees

Mysql

2022-06-27

1 310

题解 | #计算商城中2021年每月的GMV#

-- 不足10 的月份前面补0： Select Right(100 + Month(需要获取月份的时间), 2) date_format(event_time,'%Y-%m') select concat(year(event_time),'-',Right(100 + Month(ev...

Mysql 数据库

2022-06-24

1 250

题解 | #2021年11月每天的人均浏览文章时长#

select date_format(in_time,'%Y-%m-%d') as dt, round(sum(timestampdiff(second,in_time,out_time))/count(distinct uid),1) as avg_viiew_len_...

Mysql

2022-06-23

5 365

题解 | #将两个 SELECT 语句结合起来（一）#

(select prod_id, quantity from OrderItems where quantity=100) union (select prod_id,quantity from OrderItems where prod_id like 'BNBG%') order by prod...

Mysql

2022-06-23

1 222

题解 | #组合 Products 表中的产品名称和 Customers 表中的顾客名称#

(SELECT cust_name, cust_contact, cust_email FROM Customers WHERE cust_state = 'MI' UNION SELECT cust_name, cust_contact, cust_email FROM Customers WHE...

Mysql

2022-06-23

0 236

题解 | #纠错4#

(SELECT cust_name, cust_contact, cust_email FROM Customers WHERE cust_state = 'MI' UNION SELECT cust_name, cust_contact, cust_email FROM Customers WHE...

Mysql

2022-06-23

1 243

题解 | #每类视频近一个月的转发量/率#

select info.tag,sum(log.if_retweet) as retweet_cut, round((sum(log.if_retweet)/count(info.tag)),3) as retweet_rate from tb_video_info info righ...

Mysql

2022-06-22

3 394

题解 | #各个视频的平均完播率#

select info.tag,concat ( round(avg(if(timestampdiff(second,log.start_time,log.end_time)>=info.duration,100, timestampdiff(second,log.start_time,log...

Mysql

2022-06-22

1 349