How to insert values ​​into a table with the help of MySQL self-calculated output?

INSERT INTO table_name(column1,column2,column3,…) Select value1,value2,value3,…;

mysql> Create table testing(id int, item_name varchar(10));
Query OK, 0 rows affected (0.15 sec)

mysql> Insert into testing (id,item_name)Select 1,'Book';
Query OK, 1 row affected (0.11 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> Insert into testing (id,item_name)Select 2,'Pen';
Query OK, 1 row affected (0.11 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from testing;

+------+-----------+
| id   | item_name |
+------+-----------+
| 1    | Book      |
| 2    | Pen       |
+------+-----------+

2 rows in set (0.00 sec)