题解 | #顾客登录名#

select cust_id,cust_name,
#upper(concat(substr(cust_name,1,2),substr(cust_city,1,3))) as user_login
upper(concat(left(cust_name,2),left(cust_city,3))) as user_login
from Customers

1.MySQL的substr和substring是一样的。都是提取字符串的子字符串https://blog.csdn.net/lanxingbudui/article/details/83782276

2.upper大写，lower小写

3.concat连接字符串https://blog.csdn.net/Ajdidfj/article/details/123246593

4.left取字符串左边几位，right取字符串右边几位