select DISTINCT user_name1, LENGTH(user_name1), CHAR_LENGTH(user_name1) from t_user_grade
length : 漢字算三個字符, 其餘算1個字符
char_length: 都算1個字符
select DISTINCT user_name1, LENGTH(user_name1), CHAR_LENGTH(user_name1) from t_user_grade
length : 漢字算三個字符, 其餘算1個字符
char_length: 都算1個字符
select UNIX_TIMESTAMP(update_time)- UNIX_TIMESTAMP(insert_time) from t_video