The problem is that when a new row is inserted, an error is returned.
type:

mysql> insert into students values(1,"goutou",18,"male",12121);

Returns:

ERROR 1136 (21S01): Column count doesn't match value count at row 1

check statement is ok. Considering the previous operation of deleting a column, two new columns are added, and the input is:

mysql> insert into students(id,name,age,gender,clc_id) values(0,"zhutou",12,"male",12121);
Query OK, 1 row affected (0.06 sec)