qq_29423387的博客

SQL_牛客SQL1 查询所有的列select * from user_profileSQL2 查询多列select device_id,gender,age,university from user_profileSQL3 查询结果去重select distinct university FROM user_profileSQL4 查询结果限制返回行数select device_idFROM user_profileLIMIT 2SQL5 将查询后的列重新命名selec

问题语句：报错内容：bug:left is xxx,right is xxx解决问题办法：where a.USER_ID=b.USER_ID改成where cast(a.USER_ID as char)=b.USER_ID