Mysql查看字段长度

length: 一个汉字是算三个字符，一个数字或字母算一个字符。
char_length: 不管汉字还是数字或者是字母都算是一个字符。

select email , length(email) from ucenter_user_info order by length(email) desc; 
select username , length(username) from ucenter_user_info order by length(username) desc;