解题思路：
 截取字符串 left(cust_contact,2),left(cust_city,3) 
 拼接字符串 concat( left(cust_contact,2),left(cust_city,3) )
 大写函数 upper(concat( left(cust_contact,2),left(cust_city,3) ))

答案：
SELECT cust_id	,cust_name	
,upper(concat( left(cust_contact,2),left(cust_city,3) )) user_login
FROM Customers