mysql查詢某一列的數據最大位元組

語法：
select 列名, length(列名) 
from 表名
where 
length(列名) = ( select max(length(列名)) from 表名);

實例：
select project_num, length(project_num) 
from project_infor_table 
where 
length(project_num) = ( select max(length(project_num)) from project_infor_table);